Stock-based Compensation (Summary of Restricted Stock Awards Vested) (Details) (USD $) Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares vested	1,717	891	366
Fair value on vesting date	$ 74,754,000	$ 34,813,000	$ 9,190,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	31,300,000	35,200,000	28,200,000
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense on restricted stock awards	$ 25,100,000
Unrecognized compensation expense on restricted stock awards, weighted average period, years	1