Employee benefit plans and stock-based compensation plans reflecting the two-for-one stock split (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2011 Y Multiplier	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance under stock-based compensation plans	28,500,000	28,500,000
Restricted stock units and performance shares granted		800,000
Employee benefit plans and stock-based compensation plans reflecting the two-for-one stock split (Textual) [Abstract]
Retirement Savings Plan employees contribution as a percentage of salary, Minimum		15.00%
Retirement Savings Plan employees contribution as a percentage of salary, Maximum		25.00%
Employers contribution as a percentage on first one percent on employees contribution		200.00%
Employers contribution as a percentage on next three percent on employees contribution		100.00%
Retirement savings plan, contribution expense		$ 25.7	$ 26.8	$ 22.0
Employees contribution to Employees Stock purchase plan as a percentage of Employees salary		10.00%
Employee stock purchase plan purchase price of shares as percentage on fair market value		95.00%
Common stock issued under employee stock purchase plan		200,000	217,000	260,000
Common stock reserved for future purchases under the employee stock purchase plan	2,400,000	2,400,000
Contribution by employee for deferred compensation plan's benefit payments from base earnings percentage		50.00%
Contribution by employee for deferred compensation plans benefit payments from specific bonus percentage		100.00%
Deferred Compensation Plan Employer Contribution as a percentage on employees total annual compensation		6.00%
Employers Contribution allocated to Hypothetical Investment In Common Stock Percentage		25.00%
Net deferred compensation plan expense		0.6	1.5	(0.6)
Reserved common stock under deferred compensation plan		5,900,000
Unearned compensation related to unvested shares for deferred compensation plan		0.3	0.3
Weighted average remaining recognition period for restricted stock and performance shares		1.5
Maximum contractual term of stock options and SSRs		10 years
Maximum multiplier used to calculate value of performance shares		2.5
Weighted average remaining recognition period for SSRs and stock options		1.5
Windfall tax benefit related to stock options exercised		28.3
Tax benefit related to employee stock compensation		17.7	18.1	16.6
Weighted average remaining contractual term of stock options and stock settled appreciation rights outstanding		4.1
Weighted average remaining contractual term of stock options and stock settled appreciation rights exercisable		3.0
Intrinsic value shares outstanding	176.1	176.1
Intrinsic value shares exercisable	148.7	148.7
Fair value of vested restricted shares		20.9	10.5	12.4
Stock options granted	1,000,000	3,300,000
Restricted Stock and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned compensation expense	37.2	37.2	16.5
Pretax compensation expense		13.9	17.5	16.2
Vesting period of stock option plan		3 years
Restricted stock units and performance shares granted	500,000
SSRs and Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned compensation expense	32.1	32.1	23.9
Pretax compensation expense		$ 34.6	$ 32.1	$ 28.6
Vesting period of stock option plan		3 years
2011 LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance under stock-based compensation plans	30,000,000	30,000,000