Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
[Line Items]
Outstanding, beginning balance, Number	774,000		625,000
Granted, Number	255,000	[1]	443,000	[1]
Weighted-average fair value	$ 42.51	[1]	$ 47.33	[1]
Forfeited, Number	(11,000)		(28,000)
Outstanding, ending balance, Number	765,000		864,000
Vested and Released [Member]
[Line Items]
Released, Number	(253,000)		(176,000)
Released, Aggregate Intrinsic Value	$ 13,562	[2]	$ 11,536	[2]
Vested but Not Released [Member]
[Line Items]
Released, Number	(29,000)
Released, Aggregate Intrinsic Value	1,244	[2]
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number	672,000
Expected to vest, Aggregate Intrinsic Value	$ 28,496	[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 final attainment of performance goals has been determined at the conclusion of the performance period, which had not occurred as of June 30, 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.