Stockholders' Equity and Stock-based Compensation (Stock Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Outstanding Shares
Beginning balance (in shares)	3,429,309	4,495,891	7,527,680
Granted (in shares)	496,145	366,786	408,225
Exercised (in shares)	(901,290)	(1,183,235)	(2,997,095)
Canceled (in shares)	(157,489)	(250,133)	(442,919)
Ending balance (in shares)	2,866,675	3,429,309	4,495,891	7,527,680
Vested and Expected to vest (in shares)	2,655,987
Exercisable (in shares)	2,099,200
Weighted Average Exercise Price
Weighted average exercise price, beginning balance (in dollars per share)	$ 31.79	$ 25.29	$ 19.25
Weighted average exercise price, granted (in dollars per share)	87.10	79.79	40.82
Weighted average exercise price, exercised (in dollars per share)	27.55	20.33	11.05
Weighted average exercise price, canceled (in dollars per share)	71.04	39.61	33.29
Weighted average exercise price, ending balance (in dollars per share)	40.54	$ 31.79	$ 25.29	$ 19.25
Vested and Expected to vest, weighted average exercise price (in dollars per share)	37.27
Exercisable, Weighted average exercise price (in dollars per share)	$ 28.39
Weighted Average Remaining Contractual Life (Years)
Weighted average remaining contractual life	6 years	6 years 4 months 24 days	6 years 7 months 6 days	6 years
Vested and Expected to vest, weighted average remaining contractual life	5 years 10 months 24 days
Exercisable, weighted average remaining contractual life	5 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 125,647	$ 149,935	$ 153,129	$ 101,717
Vested and Expected to vest, aggregate intrinsic value	124,592
Exercisable, aggregate intrinsic value	$ 115,916