Stock-Based Compensation Restricted Stock Units Summary (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
[Line Items]
Outstanding, beginning balance, Number		682	658
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	[1]	319	320
Weighted-average fair value	[1]	$ 35.30	$ 35.49
Forfeited, Number		(36)	(21)
Outstanding, ending balance, Number		683	696
Vested and Released [Member]
[Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		282	261
Released, Aggregate Intrinsic Value	[2]	$ 11,593	$ 12,818
Vested but Not Released [Member]
[Line Items]
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures		5
Released, Aggregate Intrinsic Value	[2]	$ 171
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number		551
Expected to vest, Aggregate Intrinsic Value	[2]	$ 18,965

[1] Restricted stock units granted in 2014 and 2015 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 June 30, 2014 and 2015, 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.