Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Per Share data	6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010
Restricted Stock Units (RSUs) [Member]
[Line Items]
Outstanding, beginning balance, Number	588		326
Granted, Number	255	[1]	210	[1]
Granted, Weighted Average Grant Date Fair Value	$ 56.64	[1]	$ 63.52	[1]
Released, Number	(192)		(75)
Released, Aggregate Intrinsic Value	$ 15,007	[2]	$ 4,965	[2]
Forfeited, Number	(5)		(12)
Outstanding, ending balance, Number	646		449
Expected to vest, Number	545
Expected to vest, Aggregate Intrinsic Value	$ 26,268	[2]

[1] These restricted stock units do not include the respective 2010 and 2011 awards under the Performance Awards 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.