Goodwill and Intangible Assets - Amortization Expense Associated with Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 1,900	$ 1,900	$ 1,900	$ 1,800	$ 1,900	$ 1,900	$ 1,800	$ 1,800	$ 13,673	[1]	$ 11,917	[1]	$ 13,535	[1]
Cost of revenues
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets									7,594		7,371		6,630
Selling, general and administrative expenses
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets									$ 6,079		$ 4,546		$ 6,905

[1] Cost of revenues and selling, general and administrative expenses exclude the amortization of intangible assets. See Note 7 to the consolidated financial statements.