Income Taxes (Details) - USD ($)	12 Months Ended
	Aug. 31, 2016	Aug. 31, 2015	Aug. 31, 2014
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income tax computed at statutory rate	$ 155,600,000	$ 120,300,000	$ 93,000,000
State income tax, net of federal income tax benefit	11,000,000	8,600,000	6,700,000
Foreign permanent differences and rate differential	(2,000,000)	(1,400,000)	(1,000,000)
Other, net	(10,800,000)	(6,000,000)	(8,800,000)
Total provision for income taxes	153,800,000	121,500,000	89,900,000
Deferred Income Tax Liabilities:
Depreciation	(22,500,000)	(9,600,000)
Goodwill and intangibles	(161,600,000)	(105,100,000)
Other liabilities	(3,700,000)	(4,200,000)
Total deferred income tax liabilities	187,800,000	118,900,000
Deferred Income Tax Assets:
Self-insurance	4,000,000	3,900,000
Pension	41,700,000	29,200,000
Deferred compensation	28,900,000	27,500,000
Net operating losses	14,300,000	15,700,000
Other accruals not yet deductible	33,500,000	18,800,000
Other assets	12,300,000	10,600,000
Total deferred income tax assets	134,700,000	105,700,000
Valuation Allowance	(16,400,000)	(15,000,000)
Net deferred income tax liabilities	(69,500,000)	(28,200,000)
Undistributed earnings and original investments in foreign subsidiaries	83,200,000
State tax credit carryforwards	1,100,000
Unrecognized tax benefits that if recognized would affect annual effective tax rate	3,900,000	2,200,000
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits balance at September 1	4,500,000	3,000,000
Additions based on tax positions related to the current year	1,000,000	800,000
Additions for tax positions of prior years	500,000	1,500,000
Reductions due to lapse of statute of limitations	(800,000)	(800,000)
Unrecognized tax benefits balance at August 31	5,200,000	4,500,000	$ 3,000,000
Total accrued interest	900,000	$ 700,000
Accruals related to income tax penalties	0
Internal Revenue Service (IRS)
Deferred Income Tax Assets:
Operating loss carryforwards	24,300,000
State and Local Jurisdiction
Deferred Income Tax Assets:
Operating loss carryforwards	12,500,000
Foreign Tax Authority
Deferred Income Tax Assets:
Operating loss carryforwards	$ 21,200,000