Receivables (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	$ 115,640		$ 113,514
Unbilled	31,250	[1]	32,487	[1]
Receivables, Gross, Current, Total	146,890		146,001
Less: allowance for doubtful accounts	(3,157)		(3,406)		(3,714)
Receivables, net	$ 143,733		$ 142,595

[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.