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           CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | |
|---|---|---|
| 
           Dec. 31, 2013 
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           Dec. 31, 2012 
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| CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME | ||
| Net income | $ 33,859 | $ 21,316 | 
| Foreign currency translation adjustments | (3,085) | (603) | 
| Comprehensive income | $ 30,774 | $ 20,713 | 
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- Definition 
          Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- 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 
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- Details 
          
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