Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Schedule of Employee Benefit Plans [Line Items]
Employer matching contribution	$ 1,895,000	$ 1,747,000	$ 1,521,000
Maximum Employer Matching Contribution, Percent of participant's Gross salary	6.00%	6.00%	6.00%
Employer Matching Contribution, Percent of Match	100.00%	100.00%	100.00%