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, 2013		Mar. 31, 2012
Restricted Stock Units (RSUs) [Member]
[Line Items]
Outstanding, beginning balance, Number	774,000		625,000
Granted, Number	237,000	[1]	374,000	[1]
Weighted-average fair value	$ 42.13	[1]	$ 48.23	[1]
Released, Number	(224,000)		(168,000)
Released, Aggregate Intrinsic Value	$ 12,084	[2]	$ 10,976	[2]
Forfeited, Number	(7,000)		(14,000)
Outstanding, ending balance, Number	780,000		817,000
Vested, Number	29,000
Vested, Aggregate Intrinsic Value	1,361	[2]
Expected to vest, Number	677,000
Expected to vest, Aggregate Intrinsic Value	$ 31,431	[2]

[1] Restricted stock units granted in 2012 and 2013 do not include awards under the Performance Award Agreement for the respective years, as these awards are not granted until attainment of annual performance goals has been determined at the conclusion of the performance period, which had not occurred as of March 31, 2012 and 2013, respectively.

[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.