Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2012
Receivables [Abstract]
Billed	$ 123,083		$ 115,640
Unbilled	35,139	[1]	31,250	[1]
Receivables, Gross, Current, Total	158,222		146,890
Less: allowance for doubtful accounts	(2,927)		(3,157)		(3,406)
Receivables, net	$ 155,295		$ 143,733

[1] Represents revenue recorded in excess of amounts billable pursuant to contract provisions and generally become billable at contractually specified dates or upon the attainment of milestones. Unbilled amounts are expected to be realized within one year.