Income Taxes - Principal Reasons for Differences from Federal Statutory Rate (Detail)	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal tax at statutory rate	35.00%	34.00%
True-up of prior year's tax provision	(2.10%)	1.40%
State tax at statutory rate	3.90%	5.50%
Permanent and other differences	0.20%	0.40%
Uncertain tax position allowance	2.40%
Effective Tax Rate	39.40%	41.30%