Stock-Based Compensation - Option Activity (Details) - Jun. 30, 2015 - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		Total
Number of Options
Outstanding at December 31, 2014		650
Granted		74
Exercised		(69)
Forfeited/canceled/expired		(8)
Outstanding at June 30, 2015		647
Vested and expected to vest at June 30, 2015		647
Exercisable on June 30, 2015		445
Weighted-Average Exercise Price
Outstanding at December 31, 2014		$ 25.56
Granted		65.54
Exercised		23.95
Forfeited/canceled/expired		20.64
Outstanding at June 30, 2015		30.35
Vested and expected to vest at June 30, 2015		30.35
Exercisable on June 30, 2015		$ 24.88
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding at June 30, 2015		5 years 3 months 28 days
Vested and expected to vest at June 30, 2015		5 years 3 months 25 days
Exercisable on June 30, 2015		4 years 9 months 17 days
Exercised		$ 2,122
Outstanding at June 30, 2015	[1]	13,761
Vested and expected to vest at June 30, 2015	[1]	13,756
Exercisable on June 30, 2015	[1]	$ 11,118

[1] The aggregate intrinsic value represents the total pre-tax value (the difference between our closing stock price on the last trading day of the second quarter of 2015 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had they all exercised their options on June 30, 2015. This amount will change based on the fair market value of our stock.