Income Taxes (Tables)
   | 
12 Months Ended | 
Sep. 30, 2011  | 
| Income Taxes | 
 
 | 
| Components of income from continuing operations before income taxes | 
| 
   
| 
   
 | 
   
 | 
 Year ended September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 2009 
 | 
   
 | 
 
| 
 Income from continuing operations before income taxes: 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 United States 
 | 
   
 | 
 $ 
 | 
 66,842 
 | 
   
 | 
 $ 
 | 
 66,162 
 | 
   
 | 
 $ 
 | 
 77,718 
 | 
   
 | 
 
| 
 Foreign 
 | 
   
 | 
 59,054 
 | 
   
 | 
 42,160 
 | 
   
 | 
 11,016 
 | 
   
 | 
 
| 
 Income from continuing operations before income taxes 
 | 
   
 | 
 $ 
 | 
 125,896 
 | 
   
 | 
 $ 
 | 
 108,322 
 | 
   
 | 
 $ 
 | 
 88,734 
 | 
   
 | 
 
 
 | 
 
 
 | 
| Provision for income taxes | 
| 
   
| 
   
 | 
   
 | 
 Year ended September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 2009 
 | 
   
 | 
 
| 
 Current provision: 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Federal 
 | 
   
 | 
 20,090 
 | 
   
 | 
 $ 
 | 
 23,712 
 | 
   
 | 
 $ 
 | 
 5,013 
 | 
   
 | 
 
| 
 State and local 
 | 
   
 | 
 4,484 
 | 
   
 | 
 5,197 
 | 
   
 | 
 1,143 
 | 
   
 | 
 
| 
 Foreign 
 | 
   
 | 
 17,422 
 | 
   
 | 
 13,188 
 | 
   
 | 
 2,266 
 | 
   
 | 
 
| 
 Total current provision 
 | 
   
 | 
 41,996 
 | 
   
 | 
 42,097 
 | 
   
 | 
 8,422 
 | 
   
 | 
 
| 
 Deferred tax expense (benefit): 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Federal 
 | 
   
 | 
 $ 
 | 
 1,572 
 | 
   
 | 
 $ 
 | 
 (1,678 
 | 
 ) 
 | 
 $ 
 | 
 21,203 
 | 
   
 | 
 
| 
 State and local 
 | 
   
 | 
 397 
 | 
   
 | 
 (278 
 | 
 ) 
 | 
 4,534 
 | 
   
 | 
 
| 
 Foreign 
 | 
   
 | 
 (211 
 | 
 ) 
 | 
 (1,216 
 | 
 ) 
 | 
 734 
 | 
   
 | 
 
| 
 Total deferred tax expense (benefit) 
 | 
   
 | 
 1,758 
 | 
   
 | 
 (3,172 
 | 
 ) 
 | 
 26,471 
 | 
   
 | 
 
| 
 Income tax expense 
 | 
   
 | 
 $ 
 | 
 43,754 
 | 
   
 | 
 $ 
 | 
 38,925 
 | 
   
 | 
 $ 
 | 
 34,893 
 | 
 
 
 | 
 
 
 | 
| Schedule of reconciliation of actual provision for income taxes and provision for income taxes resulted from the use of the federal statutory income tax | 
| 
   
  
| 
   
 | 
   
 | 
 Year ended September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 2009 
 | 
   
 | 
 
| 
 Federal income tax provision at statutory rate of 35%  
 | 
   
 | 
 $ 
 | 
 44,063 
 | 
   
 | 
 $ 
 | 
 37,913 
 | 
   
 | 
 $ 
 | 
 31,057 
 | 
   
 | 
 
| 
 Valuation allowance on net operating loss carryforwards  
 | 
   
 | 
 (16 
 | 
 ) 
 | 
 (33 
 | 
 ) 
 | 
 (330 
 | 
 ) 
 | 
 
| 
 Permanent items 
 | 
   
 | 
 314 
 | 
   
 | 
 1,263 
 | 
   
 | 
 512 
 | 
   
 | 
 
| 
 State income taxes, net of federal benefit  
 | 
   
 | 
 3,175 
 | 
   
 | 
 3,153 
 | 
   
 | 
 3,811 
 | 
   
 | 
 
| 
 Foreign taxes 
 | 
   
 | 
 (3,644 
 | 
 ) 
 | 
 (2,177 
 | 
 ) 
 | 
 (518 
 | 
 ) 
 | 
 
| 
 Other 
 | 
   
 | 
 (138 
 | 
 ) 
 | 
 (1,194 
 | 
 ) 
 | 
 361 
 | 
   
 | 
 
| 
 Income tax expense 
 | 
   
 | 
 $ 
 | 
 43,754 
 | 
   
 | 
 $ 
 | 
 38,925 
 | 
   
 | 
 $ 
 | 
 34,893 
 | 
   
 | 
 
 
 | 
 
 
 | 
| Significant items comprising the Company's deferred tax assets and liabilities | 
| 
   
  
| 
   
 | 
   
 | 
 As of September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 
| 
 Deferred tax assetscurrent: 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Costs deductible in future periods  
 | 
   
 | 
 $ 
 | 
 9,315 
 | 
   
 | 
 $ 
 | 
 8,060 
 | 
   
 | 
 
| 
 Deferred revenue 
 | 
   
 | 
 12,675 
 | 
   
 | 
 13,177 
 | 
   
 | 
 
| 
 Total deferred tax assetscurrent  
 | 
   
 | 
 21,990 
 | 
   
 | 
 21,237 
 | 
   
 | 
 
| 
 Deferred tax liabilitiescurrent: 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Accounts receivableunbilled  
 | 
   
 | 
 2,734 
 | 
   
 | 
 6,701 
 | 
   
 | 
 
| 
 Other 
 | 
   
 | 
  
 | 
   
 | 
 1,246 
 | 
   
 | 
 
| 
 Total deferred tax liabilitiescurrent: 
 | 
   
 | 
 2,734 
 | 
   
 | 
 7,947 
 | 
   
 | 
 
| 
 Net deferred tax assetcurrent  
 | 
   
 | 
 $ 
 | 
 19,256 
 | 
   
 | 
 $ 
 | 
 13,290 
 | 
   
 | 
 
| 
 Deferred tax assetsnon-current: 
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Non-cash equity compensation  
 | 
   
 | 
 $ 
 | 
 4,012 
 | 
   
 | 
 $ 
 | 
 4,852 
 | 
   
 | 
 
| 
 Costs deductible in future periods  
 | 
   
 | 
 2,567 
 | 
   
 | 
 5,093 
 | 
   
 | 
 
| 
 Net operating loss carryforwards  
 | 
   
 | 
 1,028 
 | 
   
 | 
 1,079 
 | 
   
 | 
 
| 
 Valuation allowance on net operating loss carryforwards  
 | 
   
 | 
 (1,028 
 | 
 ) 
 | 
 (1,079 
 | 
 ) 
 | 
 
| 
 Deferred contract costs  
 | 
   
 | 
 101 
 | 
   
 | 
 464 
 | 
   
 | 
 
| 
 Other 
 | 
   
 | 
 1,167 
 | 
   
 | 
  
 | 
   
 | 
 
| 
 Total deferred tax assetsnon-current  
 | 
   
 | 
 7,847 
 | 
   
 | 
 10,409 
 | 
   
 | 
 
| 
 Total deferred tax liabilitiesnon-current  
 | 
   
 | 
   
 | 
   
 | 
   
 | 
   
 | 
 
| 
 Amortization of goodwill and intangible assets  
 | 
   
 | 
 3,976 
 | 
   
 | 
 2,228 
 | 
   
 | 
 
| 
 Property and equipment  
 | 
   
 | 
 10,767 
 | 
   
 | 
 6,723 
 | 
   
 | 
 
| 
 Capitalized software  
 | 
   
 | 
 4,237 
 | 
   
 | 
 4,332 
 | 
   
 | 
 
| 
 Other 
 | 
   
 | 
 80 
 | 
   
 | 
 228 
 | 
   
 | 
 
| 
 Total deferred tax liabilitynon-current  
 | 
   
 | 
 $ 
 | 
 19,060 
 | 
   
 | 
 $ 
 | 
 13,511 
 | 
   
 | 
 
| 
 Net deferred tax liabilitynon-current  
 | 
   
 | 
 $ 
 | 
 11,213 
 | 
   
 | 
 $ 
 | 
 3,102 
 | 
   
 | 
 
 
 | 
 
 
 | 
| Components of noncurrent deferred tax assets (liabilities) | 
| 
   
  
| 
   
 | 
   
 | 
 As of September 30, 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 
| 
 Long-term assets 
 | 
   
 | 
 $ 
 | 
 732 
 | 
   
 | 
 $ 
 | 
 1,844 
 | 
   
 | 
 
| 
 Long-term liabilities  
 | 
   
 | 
 11,945 
 | 
   
 | 
 4,946 
 | 
   
 | 
 
| 
 Net deferred tax liabilitynon-current  
 | 
   
 | 
 $ 
 | 
 (11,213 
 | 
 ) 
 | 
 $ 
 | 
 (3,102 
 | 
 ) 
 | 
 
 
 | 
 
 
 | 
| Schedule of reconciliation of the beginning and ending amount of gross unrecognized tax benefits | 
| 
   
  
| 
   
 | 
   
 | 
 Year Ended 
September 30 
 | 
   
 | 
 
| 
   
 | 
   
 | 
 2011 
 | 
   
 | 
 2010 
 | 
   
 | 
 2009 
 | 
   
 | 
 
| 
 Balance at beginning of year  
 | 
   
 | 
 $ 
 | 
 1,553 
 | 
   
 | 
 $ 
 | 
 2,045 
 | 
   
 | 
 $ 
 | 
 2,291 
 | 
   
 | 
 
| 
 Additions based on tax positions related to the current year  
 | 
   
 | 
  
 | 
   
 | 
 45 
 | 
   
 | 
  
 | 
   
 | 
 
| 
 Reductions for tax positions of prior years  
 | 
   
 | 
  
 | 
   
 | 
 (196 
 | 
 ) 
 | 
  
 | 
   
 | 
 
| 
 Lapse of statute of limitations  
 | 
   
 | 
 (381 
 | 
 ) 
 | 
  
 | 
   
 | 
 (68 
 | 
 ) 
 | 
 
| 
 Settlements 
 | 
   
 | 
  
 | 
   
 | 
 (341 
 | 
 ) 
 | 
 (178 
 | 
 ) 
 | 
 
| 
 Balance at end of year  
 | 
   
 | 
 $ 
 | 
 1,172 
 | 
   
 | 
 $ 
 | 
 1,553 
 | 
   
 | 
 $ 
 | 
 2,045 
 | 
 
 
 | 
 
 
 |