Income Taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Income From Continuing Operations Before Taxes [Abstract]
US	$ 234,035	$ 217,947	$ 220,005
Non US	29,842	21,548	7,727
Income from continuing operations before income taxes	263,877	239,495	227,732
Federal:
Current	84,119	83,791	78,817
Deferred	278	(3,714)	168
Federal Income Tax Expense (Benefit), Continuing Operations	84,397	80,077	78,985
State:
Current	7,186	6,664	8,151
Deferred	(128)	473	(2)
State and Local Income Tax Expense (Benefit), Continuing Operations	7,058	7,137	8,149
Foreign:
Current	5,818	1,916	1,651
Deferred	229	(1,262)	(599)
Foreign Income Tax Expense (Benefit), Continuing Operations	6,047	654	1,052
Income Tax Expense (Benefit), Total	97,502	87,868	88,186
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Federal statutory rate	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit	1.70%	2.00%	3.50%
Foreign	(0.40%)	(1.70%)	(0.80%)
Compensation and fringe benefits	0.20%	0.20%	0.30%
Other differences	0.40%	1.20%	0.70%
Effective tax rate	36.90%	36.70%	38.70%
Deferred tax assets:
Allowance for doubtful accounts	1,063	982
Accrued compensation and benefits	18,249	13,898
State taxes	1,488	1,358
Accrued other	3,006	1,884
Deferred revenue		1,910
Property and equipment	3,378	8,693
State net operating losses	398	327
Long-term note write off		423
Federal tax benefit	5,758	4,348
Total gross deferred tax assets	33,340	33,823
Less valuation allowance	(948)	(787)
Net deferred tax assets	32,392	33,036
Deferred tax liabilities:
Vehicle pooling costs	(4,956)	(9,414)
Prepaid insurance	(1,397)	(671)
Deferred revenue	(1,721)
Intangibles and goodwill	(25,031)	(23,640)
Workers compensation	(359)
Total gross deferred tax liabilities	33,464	33,725
Net deferred tax liability	$ (1,072)	$ (689)