Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Current:
Federal	$ 121,418	$ 113,057	$ 97,866
Foreign	9,414	9,997	10,925
State	14,637	17,727	16,692
Total current portion	145,469	140,781	125,483
Deferred:
Federal	(335)	13,932	4,920
Foreign	(895)	(2,822)	(2,888)
State	447	(375)	364
Total deferred portion	(783)	10,735	2,396
Total provision for income taxes	$ 144,686	$ 151,516	$ 127,879
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)	2.70%	2.80%	3.40%
Effect of foreign operations (as a percent)	(0.50%)	(0.60%)	(0.40%)
Effect of limited restructuring (as a percent)			(2.80%)
Other, net (as a percent)	(0.20%)	(0.50%)	0.20%
Effective tax rate (as a percent)	37.00%	36.70%	35.40%