Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Sep. 30, 2016
Payables and Accruals [Abstract]
Compensation	$ 111,410	$ 154,028
Accrued interest payable	23,629	20,409
Cost of revenue related liabilities	17,639	19,351
Consulting and professional fees	16,083	18,001
Facilities related liabilities	8,600	7,382
Sales and marketing incentives	4,509	6,508
Sales and other taxes payable	2,083	2,708
Other	10,975	9,272
Total	$ 194,928	$ 237,659