Stock-Based Compensation - Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Number of Options (in 000's)
Outstanding at beginning of period (in shares) | shares	652
Granted (in shares) | shares	92
Exercised (in shares) | shares	(35)
Forfeited/canceled/expired (in shares) | shares	(18)
Outstanding at end of period (in shares) | shares	691	[1]
Vested and expected to vest at end of period (in shares) | shares	691	[1]
Exercisable at end of period (in shares) | shares	424	[1]
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 39.27
Granted (in dollars per share) | $ / shares	62.70
Exercised (in dollars per share) | $ / shares	24.41
Forfeited/canceled/expired (in dollars per share) | $ / shares	28.08
Outstanding at end of period (in dollars per share) | $ / shares	43.41	[1]
Vested and expected to vest at end of period (in dollars per share) | $ / shares	43.41	[1]
Exercisable at end of period (in dollars per share) | $ / shares	$ 35.97	[1]
Weighted-Average Remaining Contractual Term (in years)
Outstanding at end of period	4 years 10 months 17 days	[1]
Vested and expected to vest at end of period	4 years 10 months 17 days	[1]
Exercisable at end of period	4 years 3 months	[1]
Exercised | $	$ 1,555
Outstanding at end of period | $	16,207	[1]
Vested and expected to vest at end of period | $	16,204	[1]
Exercisable at end of period | $	$ 13,092	[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 2017 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, 2017. This amount will change based on the fair market value of our stock.