Selected Unaudited Consolidated Financial Results (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Quarterly Financial Information [Line Items]
Amortization expense	$ 1,700	$ 1,700	$ 1,700	$ 1,500	$ 500	$ 100	$ 100	$ 600	$ 13,535	[1]	$ 6,944	[1]	$ 7,741	[1]

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