Stock-Based Compensation Restricted Stock Units Summary (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
[Line Items]
Outstanding, beginning balance, Number		756	682
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	[1]	172	315
Weighted average fair value	[1]	$ 40.02	$ 35.30
Forfeited, Number		(30)	(22)
Outstanding, ending balance, Number		636	709
Vested and Released [Member]
[Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		262	266
Released, Aggregate Intrinsic Value	[2]	$ 10,098	$ 10,888
Vested but Not Released [Member]
[Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		5
Released, Aggregate Intrinsic Value	[2]	$ 207
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number		506
Expected to vest, Aggregate Intrinsic Value	[2]	$ 21,106

[1] Restricted stock units granted in 2015 and 2016 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, 2015 and 2016, 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.