Stock-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended						12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 2007 Stock Inventive Plan [Member]	Jun. 15, 2010 2007 Stock Inventive Plan [Member]	Jun. 14, 2010 2007 Stock Inventive Plan [Member]	Dec. 31, 2011 2001 Stock Inventive Plan [Member]	Mar. 31, 2011 Restricted Stock Units [Member]	Dec. 31, 2011 Restricted Stock Units [Member]	Dec. 31, 2011 Restricted Stock Awards [Member]	Dec. 31, 2010 Restricted Stock Awards [Member]	Dec. 31, 2009 Restricted Stock Awards [Member]	Dec. 31, 2011 Non-Vested Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of base shares authorized								273,411
Number of shares granted by Board of Directors								264,750		143,200
Number of shares, net of cancellations, granted by Board of Directors				2,855,890
Stock incentive plan, vesting period in years				four						four
Stock incentive plan, expiration period in years				10
Maximum number of shares that may be issued for maximum performance								546,822
Number of shares of common stock authorized under the plan				5,179,393		3,179,393
Additional number of shares of common stock authorized under the plan					2,000,000
Vesting percentage on year two									50.00%
Vesting percentage on year three									25.00%
Vesting percentage on year four									25.00%
Option granted, net of cancellation				416,500			6,438,172
Number of options exercised	1,207,555						5,225,812
Intrinsic value of options exercised	$ 15,100,000	$ 11,300,000	$ 2,300,000
Tax benefits from options exercised	5,300,000	3,900,000	800,000
Cash received from option exercises	11,400,000	7,400,000	1,600,000
Unrecognized compensation expense										9,500,000			200,000
Weighted-average period for recognition of compensation cost, years										2.5			1.7
Total fair value of options vested														800,000	1,500,000	1,500,000
Total fair value of restricted stock granted										3,300,000
Weighted-average grant date fair value of restricted stock								$ 16.82		$ 23.13
Total fair value of restricted stock vested										5,700,000	3,100,000	3,600,000
Stock-based compensation expense	$ 9,324,000	$ 6,037,000	$ 4,620,000							$ 5,900,000	$ 4,900,000	$ 3,100,000		$ 500,000	$ 1,100,000	$ 1,500,000