Share-Based Payments (Details) (USD $) In Millions, except Share data, unless otherwise specified			1 Months Ended		12 Months Ended						12 Months Ended		12 Months Ended					1 Months Ended		12 Months Ended				12 Months Ended
	Aug. 31, 2011	Nov. 30, 2001 Long-Term Incentive Plan [Member]	Oct. 31, 2007 Amended Plan	Oct. 31, 2003 Amended Plan	Aug. 31, 2011 Amended Plan Stock Options years	Aug. 31, 2011 Amended Plan Restricted Stock	Aug. 31, 2010 Amended Plan Restricted Stock	Aug. 31, 2009 Amended Plan Restricted Stock	Oct. 31, 2003 Amended Plan Maximum	Nov. 30, 2001 Directors' Plan	Aug. 31, 2011 Directors' Plan Stock Options years	Jan. 31, 2007 Nonemployee Directors' Stock Option Plan, Amended [Member] Stock Options	Aug. 31, 2011 Individual Employee Plan Restricted Stock	Aug. 31, 2010 Individual Employee Plan Restricted Stock	Aug. 31, 2009 Individual Employee Plan Restricted Stock	Aug. 31, 2011 Employee Stock Purchase Plan	Aug. 31, 2011 Directors' Deferred Compensation Plan Restricted Stock Units (RSUs)	Jun. 28, 2006 Directors' Deferred Compensation Plan Restricted Stock Units (RSUs) Minimum	Aug. 31, 2011 Supplemental Deferred Savings Plan Restricted Stock Units (RSUs)	Aug. 31, 2011 Stock Options years	Aug. 31, 2010 Stock Options years	Aug. 31, 2009 Stock Options years	Aug. 31, 2008 Stock Options	Aug. 31, 2011 Stock Options Minimum	Aug. 31, 2010 Stock Options Minimum	Aug. 31, 2009 Stock Options Minimum	Aug. 31, 2011 Stock Options Maximum	Aug. 31, 2010 Stock Options Maximum	Aug. 31, 2009 Stock Options Maximum	Aug. 31, 2011 Stock Options $10.00 - $15.00 (average life - 0.9 years) years	Aug. 31, 2011 Stock Options $15.01 - $20.00 (average life - 3.2 years) years	Aug. 31, 2011 Stock Options $20.01 - $25.00 (average life - 6.7 years) years	Aug. 31, 2011 Stock Options $25.01 - $30.00 (average life - 5.2 years) years	Aug. 31, 2011 Stock Options $30.01 - $40.00 (average life - 9.1 years) years	Aug. 31, 2011 Restricted Stock years	Aug. 31, 2010 Restricted Stock	Aug. 31, 2011 $10.00 - $15.00 (average life - 0.9 years)	Aug. 31, 2011 $15.01 - $20.00 (average life - 3.2 years)	Aug. 31, 2011 $20.01 - $25.00 (average life - 6.7 years)	Aug. 31, 2011 $25.01 - $30.00 (average life - 5.2 years)	Aug. 31, 2011 $30.01 - $40.00 (average life - 9.1 years)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance		8,000,000								300,000						1,500,000
Increase in the number of shares available for grant			500,000	5,000,000
Number of shares available for grant without shareholder approval									3,000,000
Number of shares available for grant with shareholders approval			2,000,000
Number of shares available for grant												0				1,100,000				2,600,000	2,900,000	3,200,000
Share-based Compensation Arrangement, Restricted Stock Awards [Abstract]
Comensation expense recognized in continuing operations						$ 8.4	$ 8.0	$ 9.0					$ 3.0	$ 1.8	$ 1.6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Beginning of period, Outstanding, Number of Shares																																			800,000
Beginning of period, Outstanding, Weighted Average Grant date Fair Value Per Share																																			$ 34.30
Granted, Number of Shares																																			400,000
Granted, Weighted Average Grant Date Fair Value Per Share																																			$ 50.00
Vested, Number of Shares																																			(300,000)
Vested, Weighted Average Grant Date Fair Value Per Share																																			$ 36.50
Forfeited, Number of Shares																																			(100,000)
Forfeited, Weighted Average Grant Date Fair Value Per Share																																			$ 38.77
End of period, Outstanding, Number of Shares						576,000							280,000																						800,000	800,000
End of period, Outstanding, Weighted Average Grant Date Fair Value Per Share																																			$ 40.68	$ 34.30
Unrecognized compensation cost																				2.7															23.2
Unrecognized compensation cost period of recognition (years)					3						1									1.3															1.7
Total fair value of shares vested																																			11.8	10.3
Share-based Compensation Arrangement, Stock Options [Abstract]
Stock option expiration period (years)					10						10
Share-based compensation vesting period (years)					3 years	4 years					1 year
Shares (whole units) granted under Director's Plan											200,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Dividend yield																								1.30%	1.50%	1.20%	1.30%	1.80%	1.40%
Expected volatility, minimum																				41.80%	40.90%	40.10%
Expected volatility, maximum																				41.80%	41.20%	40.30%
Risk-free interest rate, minimum																				1.20%	2.10%	1.90%
Risk-free interest rate, maximum																				1.20%	2.50%	2.60%
Expected life of options																				5	5	5
Weighted-average fair value of options																								$ 16.95	$ 11.19	$ 7.53	$ 16.95	$ 13.39	$ 11.13
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning of period, Outstanding, Number of Shares																				1,500,000	1,700,000	1,600,000
Beginning of period, Outstanding, Weighted Average Exercise Price																				$ 27.78	$ 24.69	$ 23.78
Granted, Number of Shares																				200,000	200,000	300,000
Granted, Weighted Average Exercise Price																				$ 50.56	$ 34.44	$ 29.21
Exercised, Number of Shares																				(300,000)	(400,000)	(100,000)
Exercised, Weighted Average Exercise Price																				$ 21.18	$ 16.73	$ 20.34
Cancelled, Number of Shares																				(100,000)	0	(100,000)
Cancelled, Weighted Average Exercise Price																				$ 39.57	$ 0.00	$ 33.59
End of period, Outstanding, Number of Shares																				1,300,000	1,500,000	1,700,000
End of period, Outstanding, Weighted Average Exercise Price																				$ 31.67	$ 27.78	$ 24.69
Exercisable, Number of Shares, Outstanding																				1,000,000	1,100,000	1,300,000	1,300,000
Exercisable, Weighted Average Exercise Price, Outstanding	$ 28.81																				$ 26.03	$ 22.09	$ 20.26
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, End of Period [Abstract]
Range of option exercise prices: lower range limit																														$ 10.00	$ 20.01	$ 30.01	$ 40.01	$ 50.01
Range of option exercise prices: upper range limit																														$ 20.00	$ 30.00	$ 40.00	$ 50.00	$ 60.00
Range of option exercise prices: average life (years)																														0.9	3.2	6.7	5.2	9.1
Range of option exercise prices: Number of Shares, Outstanding																																					100,000	500,000	500,000	100,000	100,000
Range of option exercise prices: Weighted Average Exercise Price, Outstanding																																					$ 13.49	$ 23.81	$ 34.89	$ 40.29	$ 50.56
Range of option exercise prices: Number of Shares, Exercisable																																					100,000	500,000	300,000	100,000	0
Range of option exercise prices: Weighted Average Exercise Price, Exercisable																																					$ 13.49	$ 23.86	$ 35.46	$ 40.29	$ 0.00
Total intrinsic value of stock options excpected to vest																				8.9	7.3
Total intrinsic value of stock options exercised																				20.0
Total intrinsic value of stock options outstanding																				19.9
Total intrinsic value of stock options exercisable																				$ 17.4
Employee discount on purchases of common stock																5.00%
Deferred compensation, deferral percentage of annual retainer																		50.00%
Deferred compensation, number of share units outstanding																	127,000		45,000