Stock-Based Compensation (Restricted Stock Units Activity) (Details) (Restricted Stock Units (RSUs) [Member], USD $)	3 Months Ended
	Mar. 31, 2012
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
RSUs outstanding, Beginning Balance, Unvested	741,043
RSUs outstanding, Beginning Balance, Vested but Deferred	20,076
RSUs outstanding, Beginning Balance, Total	761,119
RSUs outstanding, Beginning Balance, Weighted Average Grant Date Valueper RSU	$ 50.66
Granted, Unvested	666
Granted, Total	666
Granted, Weighted Average Grant Date Valueper RSU	$ 59.98
Dividend equivalents, Unvested	1,278
Dividend equivalents, Vestedd but Deferred	0
Dividend equivalents, Total	1,278
Dividend equivalents, Weighted Average Grant Date Valueper RSU	$ 50.66
Vested, Unvested	(9,879)
Vested, Total	(9,879)
Vested, Weighted Average Grant Date Valueper RSU	$ 52.94
Vested but deferred, Unvested	0
Vested but deferred, Vested but Deferred	0
Vested but deferred, Total	0
Issued, Vested but Deferred	0
Issued, Total	0
Issued, Weighted Average Grant Date Valueper RSU	$ 0.00
Forfeited, Unvested	(8,765)
Forfeited, Total	(8,765)
Forfeited, Weighted Average Grant Date Valueper RSU	$ 43.76
RSUs outstanding, Ending Balance, Unvested	724,343
RSUs outstanding, Ending Balance, Vested but Deferred	20,076
RSUs outstanding, Ending Balance, Total	744,419
RSUs outstanding, Ending Balance, Weighted Average Grant Date Valueper RSU	$ 50.72