Employee Benefit Plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Purchase price of common stock as percentage of market value	95.00%
Performance period	1 year
Subsequent service period	6 months
Minimum percentage that will ultimately vest under performance-based restricted stock awards based on performance target	0.00%
Maximum percentage that will ultimately vest under performance-based restricted stock awards based on performance target	150.00%
Weighted-average remaining requisite vesting period	18 months
Repurchases of common stock	14.6		14.2		18.2
Total stock-based compensation	$ 78.7		$ 76.3		$ 67.6
Total stock-based compensation - related tax benefit	29.0		28.2		22.3
Aggregate intrinsic value of stock options outstanding	245.0
Stock options remaining outstanding period	4 years 1 month 6 days
Aggregate intrinsic value of stock options exercisable	221.7
Stock options remaining exercisable period	3 years 4 months 24 days
Aggregate intrinsic value of stock options exercised	83.8		95.7		29.1
Number of shares issued in connection with the employees stock purchase plan					1.4
Period of U.S. Treasury rate, in years	10 years
Award requisite service period, in years	3 years
Accumulated benefit obligation	1,399.9		1,167.4
Pension costs included in accumulated other comprehensive income and not yet recognized in net period benefit cost	273.1		185.8		264.7
Compensation expense recognition			Compensation expense is recognized on a straight-line basis over the vesting period
Plan contribution in current period	91.6
Expected future plan contribution in July 2012	125.0
Expected future plan contribution in fiscal 2013	8.3
Expected future plan benefit payments - 2013	48.2
Expected future plan benefit payments - 2014	52.8
Expected future plan benefit payments - 2015	60.4
Expected future plan benefit payments - 2016	67.4
Expected future plan benefit payments - 2017	77.4
Expected future plan benefit payments - 2018 to 2022	525.7
Employee contribution percentage to retirement and saving plan	35.00%
Highly compensated employee contribution percentage to retirement and saving plan	10.00%
Retirement and savings plan - company match of employee contributions		65.9		57.5		55.8
Stock Options Granted Prior To July 2008 [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock options - term in years for stock options granted prior to July 1, 2008	10 years
Vesting term of performance-based restricted stock	5 years
Stock Options Granted After July 2008 [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock options - term in years for stock options granted prior to July 1, 2008	10 years
Vesting term of performance-based restricted stock	4 years
Share Repurchase Program [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Repurchases of common stock	14.6		14.2
Nonvested Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Weighted-average remaining requisite vesting period	1 year 9 months 18 days
Total remaining unrecognized compensation cost	8.8
Nonvested Restricted Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Weighted-average remaining requisite vesting period	1 year
Total remaining unrecognized compensation cost	40.5
Net Actuarial And Other Loss Net Of Tax [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pension costs included in accumulated other comprehensive income and not yet recognized in net period benefit cost	411.0
Pension costs in accumulated other comprehensive income amortized into net period benefit cost over the next fiscal year	29.3
Transition Obligation Net Of Tax [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pension costs included in accumulated other comprehensive income and not yet recognized in net period benefit cost	0.7
Pension costs in accumulated other comprehensive income amortized into net period benefit cost over the next fiscal year	0.2
Prior Service Cost Net Of Tax [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pension costs included in accumulated other comprehensive income and not yet recognized in net period benefit cost	6.2
Pension costs in accumulated other comprehensive income amortized into net period benefit cost over the next fiscal year	$ 1.4