Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $)	6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011
Restricted Stock Units (RSUs) [Member]
[Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 30,300,000
Outstanding, beginning balance, Number	625,000		588,000
Granted, Number	443,000	[1]	255,000	[1]
Granted, Weighted Average Grant Date Fair Value	$ 47.33	[1]	$ 56.64	[1]
Released, Number	(176,000)		(192,000)
Released, Aggregate Intrinsic Value	11,536,000	[2]	15,007,000	[2]
Forfeited, Number	(28,000)		(5,000)
Outstanding, ending balance, Number	864,000		646,000
Vested, Number	47,000
Vested, Aggregate Intrinsic Value	1,945,000	[2]
Expected to vest, Number	782,000
Expected to vest, Aggregate Intrinsic Value	$ 32,265,000	[2]

[1] These restricted stock units do not include the respective 2011 and 2012 awards under the Performance Award Agreement, which are not eligible for vesting as of June 30 of each respective year.

[2] The aggregate intrinsic value is the market value of the stock, before applicable income taxes, based on the closing price on the stock release dates or at the end of the period for restricted stock units expected to vest.