| 
           CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $) 
        In Thousands, except Share data, unless otherwise specified  | 
        
           Common Stock 
         | 
        
           Accumulated Other Comprehensive Income/(Loss) 
         | 
        
           Retained Earnings 
         | 
        
           Noncontrolling Interest 
         | 
        
           Total 
         | 
      
|---|---|---|---|---|---|
| Balance at Sep. 30, 2013 | 
$ 415,271us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
$ 7,987us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        
$ 106,250us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
$ 267us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        $ 529,775us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 
| Balance (in shares) at Sep. 30, 2013 | 
68,525us-gaap_CommonStockSharesOutstanding / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        ||||
| Increase (Decrease) in Shareholders' Equity | |||||
| Net income | 
33,859us-gaap_ProfitLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
(504)us-gaap_ProfitLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        33,355us-gaap_ProfitLoss | ||
| Foreign currency translation | 
(3,085)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        (3,085)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | |||
| Cash dividends | 
(3,085)us-gaap_DividendsCommonStockCash / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        (3,085)us-gaap_DividendsCommonStockCash | |||
| Dividends on RSUs | 
125us-gaap_DividendsShareBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
(125)us-gaap_DividendsShareBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        |||
| Repurchases of common stock | 
(22,492)us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        (22,492)us-gaap_StockRepurchasedDuringPeriodValue | |||
| Repurchases of common stock (in shares) | 
(506)us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        (500,000)us-gaap_StockRepurchasedDuringPeriodShares | |||
| Stock compensation expense | 
4,081us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        4,081us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue | |||
| Stock options exercised | 
327us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        327us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised | |||
| Stock options exercised (in shares) | 
38us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        ||||
| Balance at Dec. 31, 2013 | 
419,804us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
4,902us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        
114,407us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
(237)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        538,876us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 
| Balance (in shares) at Dec. 31, 2013 | 
68,057us-gaap_CommonStockSharesOutstanding / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        ||||
| Balance at Sep. 30, 2014 | 
429,857us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
230us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        
125,875us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
223us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        556,185us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 
| Balance (in shares) at Sep. 30, 2014 | 
66,613us-gaap_CommonStockSharesOutstanding / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        66,613,000us-gaap_CommonStockSharesOutstanding | |||
| Increase (Decrease) in Shareholders' Equity | |||||
| Net income | 
41,861us-gaap_ProfitLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
489us-gaap_ProfitLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        42,350us-gaap_ProfitLoss | ||
| Foreign currency translation | 
(10,480)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        (10,480)us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | |||
| Cash dividends | 
(2,962)us-gaap_DividendsCommonStockCash / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        (2,962)us-gaap_DividendsCommonStockCash | |||
| Dividends on RSUs | 
99us-gaap_DividendsShareBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
(99)us-gaap_DividendsShareBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        |||
| Repurchases of common stock | 
(30,618)us-gaap_StockRepurchasedDuringPeriodValue / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        (30,618)us-gaap_StockRepurchasedDuringPeriodValue | |||
| Repurchases of common stock (in shares) | 
(753)us-gaap_StockRepurchasedDuringPeriodShares / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        (800,000)us-gaap_StockRepurchasedDuringPeriodShares | |||
| Stock compensation expense | 
3,966us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        3,966us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue | |||
| Balance at Dec. 31, 2014 | 
$ 433,922us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        
$ (10,250)us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember  | 
        
$ 134,057us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember  | 
        
$ 712us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest / us-gaap_StatementEquityComponentsAxis = us-gaap_NoncontrollingInterestMember  | 
        $ 558,441us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 
| Balance (in shares) at Dec. 31, 2014 | 
65,860us-gaap_CommonStockSharesOutstanding / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember  | 
        65,860,000us-gaap_CommonStockSharesOutstanding | 
| X | ||||||||||
| 
             
- Definition 
          This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation". Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of paid and unpaid common stock dividends declared with the form of settlement in cash. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of paid and unpaid cash, stock, and paid-in-kind (PIK) dividends declared and applicable to holders of share-based compensation, for example, but not limited to, non-vested shares, stock options, or restricted stock units. No definition available. 
  | 
        
| X | ||||||||||
| 
             
- Details 
          
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Number of share options (or share units) exercised during the current period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Value of stock issued as a result of the exercise of stock options. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
        
| X | ||||||||||
| 
             
- Definition 
          Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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