Stock-Based Compensation Restricted Stock Units Summary (Details) (Restricted Stock Units (RSUs) [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
[Line Items]
Outstanding, beginning balance, Number	774		625
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	255	[1]	452	[1]
Weighted-average fair value	$ 42.51	[1]	$ 47.29	[1]
Forfeited, Number	(27)		(34)
Outstanding, ending balance, Number	742		836
Vested and Released [Member]
[Line Items]
Released, Number	(260)		(207)
Released, Aggregate Intrinsic Value	$ 13,860	[2]	$ 12,835	[2]
Vested but Not Released [Member]
[Line Items]
Released, Number	(29)
Released, Aggregate Intrinsic Value	1,256	[2]
Expected to Vest [Member]
[Line Items]
Outstanding, ending balance, Number	661
Expected to vest, Aggregate Intrinsic Value	$ 28,297	[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 September 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.