Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Per Share data	9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010
Restricted Stock Units (RSUs) [Member]
[Line Items]
Outstanding, beginning balance, Number	588		326
Granted, Number	286	[1]	215	[1]
Granted, Weighted Average Grant Date Fair Value	$ 54.82	[1]	$ 63.42	[1]
Released, Number	(201)		(78)
Released, Aggregate Intrinsic Value	$ 15,739	[2]	$ 5,216	[2]
Forfeited, Number	(37)		(14)
Outstanding, ending balance, Number	636		449
Expected to vest, Number	544
Expected to vest, Aggregate Intrinsic Value	$ 16,040	[2]

[1] These restricted stock units do not include the respective 2010 and 2011 awards under the Performance Award Agreement, which are not eligible for vesting as of September 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.