Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Restricted Stock Units (RSUs) [Member]
[Line Items]
Outstanding, beginning balance, Number	625,000		588,000
Granted, Number	374,000	[1]	253,000	[1]
Granted, Weighted Average Grant Date Fair Value	$ 48.23	[1]	$ 56.67	[1]
Released, Number	(168,000)		(127,000)
Released, Aggregate Intrinsic Value	$ 10,976	[2]	$ 8,857	[2]
Forfeited, Number	(14,000)		(2,000)
Outstanding, ending balance, Number	817,000		712,000
Expected to vest, Number	733,000
Expected to vest, Aggregate Intrinsic Value	$ 33,290	[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 March 31 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.