Share-Based Employee Compensation Plans and Other Compensation and Benefit Plans (Restricted Stock Activity) (Details) (Restricted Stock [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock [Member]
Compensation expense for benefit plans	$ 1.7	$ 0.9	$ 0.5
Income tax benefit from compensation expense for benefit plans	0.6	0.4	0.2
Total fair value of shares vested (at vest date)	$ 2.6	$ 1.6	$ 0.7
Shares of common stock awarded under compensation and benefit plans, shares (in thousands)	49.9	41.1	21.8
Average grant-date fair value of shares issued during the period in compensation and benefit plans other than stock options	$ 56.18	$ 39.57	$ 33.36