Reportable Segment and Major Concentrations Data - Pre-tax Earnings Table (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Sales Information [Line Items]
Segment operating income	$ 57,314	$ 49,296	$ 40,033
Interest income	44	42	115
Other, net	4	378	352
Earnings Before Income Taxes	57,362	49,716	40,500
Operating Segments [Member]
Sales Information [Line Items]
Segment operating income	57,314	49,296	40,033
Interest income	44	42	115
Other, net	4	378	352
Earnings Before Income Taxes	$ 57,362	$ 49,716	$ 40,500