Stock-Based Compensation (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Stock Options
Stock-Based Compensation
Total unrecorded stock-based compensation expense for unvested stock options shares, net of expected forfeitures	$ 53.5
Weighted average period of total unrecorded stock-based compensation expense for unvested stock options shares, net of expected forfeitures	2 years 8 months 12 days
Cash received for stock options exercised under all stock-based compensation arrangements	76.3
Restricted Stock
Stock-Based Compensation
Total unrecorded stock-based compensation expense for unvested stock options shares, net of expected forfeitures	$ 10.0
Weighted average period of total unrecorded stock-based compensation expense for unvested stock options shares, net of expected forfeitures	1 year 3 months 18 days