CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 62,849	$ 53,477	$ 42,580
Other comprehensive income (loss)
Foreign currency translation	237	1,877	(663)
Actuarial gain on unfunded pension liability adjustment, net of tax	139	228	21
Total comprehensive income	$ 63,225	$ 55,582	$ 41,938