Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
[Line Items]
Outstanding, beginning balance, Number	658		774
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	308	[1]	237	[1]
Weighted-average fair value	$ 35.38	[1]	$ 42.13	[1]
Forfeited, Number	(3)		(7)
Outstanding, ending balance, Number	727		780
Vested and Released [Member]
[Line Items]
Released, Number	(236)		(224)
Released, Aggregate Intrinsic Value	$ 11,666	[2]	$ 12,084	[2]
Vested but Not Released [Member]
[Line Items]
Released, Number	(8)
Released, Aggregate Intrinsic Value	300	[2]
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number	605
Expected to vest, Aggregate Intrinsic Value	$ 21,503	[2]

[1] Restricted stock units granted in 2013 and 2014 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, 2013 and 2014, 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.