Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Current:
Federal	$ 87,088	$ 113,023	$ 121,418
Foreign	8,795	9,531	9,414
State	13,816	13,686	14,637
Total current portion	109,699	136,240	145,469
Deferred:
Federal	20,915	7,963	(335)
Foreign	(932)	(1,461)	(895)
State	1,436	655	447
Total deferred portion	21,419	7,157	(783)
Total provision for income taxes	$ 131,118	$ 143,397	$ 144,686
Reconciliation between the U.S. statutory federal income tax rate and the effective income tax rate
Statutory tax rate (as a percent)	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit (as a percent)	2.90%	2.70%	2.70%
Effect of foreign operations (as a percent)	(0.40%)	(0.10%)	(0.50%)
Other, net (as a percent)	(0.50%)	0.30%	(0.20%)
Effective tax rate (as a percent)	37.00%	37.90%	37.00%