Quarterly report pursuant to Section 13 or 15(d)

Business combinations (Schedule of Assets and Liabilities Recorded in the Company's Financial Statements) (Details)

v3.7.0.1
Business combinations (Schedule of Assets and Liabilities Recorded in the Company's Financial Statements) (Details) - USD ($)
$ in Thousands
 6 Months Ended
Feb. 29, 2016
Mar. 31, 2017
Sep. 30, 2016
Business Acquisition [Line Items]      
Goodwill   $ 395,011 $ 397,558
Ascend Management Innovations LLC      
Business Acquisition [Line Items]      
Fair value of consideration $ 44,100 44,069  
Billed and unbilled receivables   4,069  
Other assets   407  
Property and equipment   707  
Deferred income taxes   557  
Intangible assets — customer relationships 22,300 22,300  
Total identifiable assets acquired   28,040  
Accounts payable and other liabilities   1,414  
Deferred revenue   554  
Total liabilities assumed   1,968  
Net identifiable assets acquired   26,072  
Goodwill $ 18,000 17,997  
Net assets acquired   44,069  
Previously Reported | Ascend Management Innovations LLC      
Business Acquisition [Line Items]      
Fair value of consideration   44,069  
Billed and unbilled receivables   4,069  
Other assets   407  
Property and equipment   707  
Deferred income taxes   0  
Intangible assets — customer relationships   22,300  
Total identifiable assets acquired   27,483  
Accounts payable and other liabilities   1,414  
Deferred revenue   554  
Total liabilities assumed   1,968  
Net identifiable assets acquired   25,515  
Goodwill   18,554  
Net assets acquired   44,069  
Purchase Accounting Adjustment | Ascend Management Innovations LLC      
Business Acquisition [Line Items]      
Fair value of consideration   0  
Billed and unbilled receivables   0  
Other assets   0  
Property and equipment   0  
Deferred income taxes   557  
Intangible assets — customer relationships   0  
Total identifiable assets acquired   557  
Accounts payable and other liabilities   0  
Deferred revenue   0  
Total liabilities assumed   0  
Net identifiable assets acquired   557  
Goodwill   (557)  
Net assets acquired   $ 0