Stock-Based Compensation Plans (Details 2) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Nonqualified Stock Options
Change in options outstanding
Options outstanding at beginning of period (in shares)	12.4
Options granted (in shares)	0.5
Options exercised (in shares)	0.4
Options expired (in shares)	0.3
Options outstanding at end of period (in shares)	12.2	12.4
Options vested or expected to vest at end of period (in shares)	12.2
Options exercisable at end of period (in shares)	10.5
Options outstanding at beginning of period weighted-average exercise price (in dollars per share)	$ 38.75
Options granted weighted-average exercise price (in dollars per share)	$ 34.26
Options exercised weighted-average exercise price (in dollars per share)	$ 18.83
Options expired weighted-average exercise price (in dollars per share)	$ 33.44
Options outstanding at end of period weighted-average exercise price (in dollars per share)	$ 39.33	$ 38.75
Options vested or expected to vest at end of period weighted-average exercise price (in dollars per share)	$ 39.34
Options exercisable at end of period weighted-average exercise price (in dollars per share)	$ 42.11
Options outstanding at end of period intrinsic value	$ 27.8
Options vested or expected to vest at end of period intrinsic value	27.8
Options exercisable at end of period intrinsic value	18.1
Total intrinsic value of options exercised	4.0	1.9	0
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Weighted-average remaining contractual life for stock options exercisable (in years)	4
Assumptions used to estimate fair value of stock options granted during period
Weighted-average expected dividend yield (as a percent)	1.60%	2.25%	4.07%
Weighted-average expected volatility (as a percent)	67.90%	66.60%	55.00%
Weighted-average risk-free interest rate (as a percent)	2.50%	2.80%	2.10%
Weighted-average expected term (in years)	6	6	6
Weighted-average estimated fair value of stock options granted (in dollars per share)	$ 18.82	$ 11.48	$ 4.07
Other nonqualified stock option disclosures
Unrecognized compensation costs	3.3
Weighted-average service period over which unrecognized compensation costs will be recognized (in years)	1.7
Cash received from stock options exercised	7.3	2.2	0.2
Tax benefits realized for the tax deductions from options exercised	$ 1.4	$ 0.5	$ 0
Nonqualified Stock Options | Range of exercise prices, Range 1
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 11.07
Upper limit of exercise price range (in dollars per share)	$ 21.69
Options outstanding at end of period (in shares)	1.9
Weighted-average remaining contractual life (in years)	7
Nonqualified Stock Options | Range of exercise prices, Range 2
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 21.70
Upper limit of exercise price range (in dollars per share)	$ 32.32
Options outstanding at end of period (in shares)	1.6
Weighted-average remaining contractual life (in years)	5
Nonqualified Stock Options | Range of exercise prices, Range 3
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 32.33
Upper limit of exercise price range (in dollars per share)	$ 42.95
Options outstanding at end of period (in shares)	3.9
Weighted-average remaining contractual life (in years)	4
Nonqualified Stock Options | Range of exercise prices, Range 4
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 42.96
Upper limit of exercise price range (in dollars per share)	$ 53.58
Options outstanding at end of period (in shares)	1.7
Weighted-average remaining contractual life (in years)	4
Nonqualified Stock Options | Range of exercise prices, Range 5
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 53.59
Upper limit of exercise price range (in dollars per share)	$ 64.22
Options outstanding at end of period (in shares)	3.1
Weighted-average remaining contractual life (in years)	6
Nonqualified Stock Options | Range of exercise prices, Total Range
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 11.07
Upper limit of exercise price range (in dollars per share)	$ 64.22
Options outstanding at end of period (in shares)	12.2
Weighted-average remaining contractual life (in years)	5
2010 Stock Incentive Plan and Stock Incentive Plan, Options
Stock-Based Compensation Plans - Disclosures
Option expiration period (in years)	10
Vesting period (in years)	3
2010 Stock Incentive Plan, Options
Change in options outstanding
Options granted (in shares)	0.5	0.8	2.2
Directors Stock Plan, Options
Stock-Based Compensation Plans - Disclosures
Contractual term of options granted	the earlier of five years from the date the participant ceases to provide service or the tenth anniversary of the date the option was granted
Number of installments in which options become exercisable	4
Installment periods over which options become exercisable after grant date	three, six and nine months anniversaries of the grant date, and on the date that the Director's full term of office expires
Change in options outstanding
Options granted (in shares)	0	0	0