Stock-Based Compensation - Option Activity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Number of Options
Outstanding at December 31, 2013	924
Granted	133
Exercised	(242)
Forfeited/canceled/expired	(15)
Outstanding at June 30, 2014	800
Vested and expected to vest at June 30, 2014	800
Exercisable on June 30, 2014	514
Weighted-Average Exercise Price
Outstanding at December 31, 2013	$ 22.04
Granted	$ 35.28
Exercised	$ 19.25
Forfeited/canceled/expired	$ 21.09
Outstanding at June 30, 2014	$ 22.86
Vested and expected to vest at June 30, 2014	$ 22.87
Exercisable on June 30, 2014	$ 24.12
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding at June 30, 2014	6 years 1 month 2 days
Vested and expected to vest at June 30, 2014	6 years 1 month 2 days
Exercisable on June 30, 2014	5 years 3 months 14 days
Exercised	$ 5,534
Outstanding at June 30, 2014	20,825	[1]
Vested and expected to vest at June 30, 2014	20,799	[1]
Exercisable on June 30, 2014	$ 12,721	[1]

[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 2014 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, 2014. This amount will change based on the fair market value of our stock.