Employee Share-Based Incentive Compensation Plans (Details 4) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended			1 Months Ended		1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	May 31, 2010 Non-Qualified Options	Dec. 31, 2011 Non-Qualified Options	Dec. 31, 2010 Non-Qualified Options	Dec. 31, 2009 Non-Qualified Options	May 31, 2010 Non-Qualified Options Before amendments Y	Jan. 31, 2007 Non-Qualified Options Before amendments Y	May 26, 2010 Non-Qualified Options Before amendments	May 31, 2010 Non-Qualified Options Amended Grant Y	May 26, 2010 Non-Qualified Options Amended Grant	Feb. 29, 2000 Incentive Options	Dec. 31, 2011 Incentive Options Y	Dec. 31, 2010 Incentive Options	Dec. 31, 2009 Incentive Options
Share-based compensation arrangement by share-based payment award
Stock-based awards, contractual term (in years)									P7Y
Vesting period (in years)									5 years					10 years
Initial exercise price (in dollars per share)									$ 650.00
Fair value									$ 27.2	$ 3.5		$ 4.4
Annual percentage increase in exercise price									5.00%
Assumptions of stock-based compensation awards
Expected volatility (as a percent)								41.00%	29.70%		34.00%			18.50%
Risk-free rate (as a percent)								1.57%	1.10%		2.43%			6.40%
Risk-free rate less the Escalator (as a percent)									4.70%
Forfeiture (as a percent)								0.00%	0.00%		0.00%
Expected dividend yield (as a percent)								0.32%	1.40%		0.32%
Expected life (in years)								3.67	7		6.67			10
Extension of contractual term (in years)											3
Exercise price (in dollar per share)												$ 742
Number of shares extinguished (in shares)												75,000
Threshold for in-the-money potential											100
Limit on value of in-the-money options over $100 million (as a percent)											50.00%
Amount amortized into income prior to the modification												18.2
Unamortized amount at modification date										9.0
Expense recognized				8.7	0.1	11.9	5.4
Granted (in shares)									200,000				81,000
Percentage increase to exercise price														6.00%
Incentive option activity
Opening balance - outstanding Options (in shares)															2,400	6,000
Exercised (in shares)	0	(2,400)	(3,600)												(2,400)	(3,600)
Ending balance - outstanding Options (in shares)																2,400
Opening balance exercisable Incentive Options (in shares)															2,400	3,000
Vested (in shares)																3,000
Ending balance exercisable Incentive Options (in shares)																2,400
Intrinsic value of Incentive options exercised															$ 0.3	$ 0.5
Exercise price - Outstanding options at the beginning of the period (in dollars per share)															$ 188.43	$ 177.76
Exercise price - outstanding Options at the end of the period (in dollars per share)																$ 188.43