Stockholders' Equity - Option Activities (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Number of Shares Underlying Outstanding Options
Outstanding, beginning balance (in shares)	4,564
Options granted (in shares)	0
Options exercised (in shares)	(309)
Options canceled (in shares)	(16)
Outstanding, ending balance (in shares)	4,239	4,564
Vested and exercisable (in shares)	2,626
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in dollars per share)	$ 42.50
Options granted (in dollars per share)	0
Options exercised (in dollars per share)	24.72
Options canceled (in dollars per share)	199.60
Outstanding, ending balance (in dollars per share)	43.23	$ 42.50
Vested and exercisable (in dollars per share)	$ 29.64
Weighted- Average Remaining Contractual Term (Years) and Aggregate Intrinsic Value of Stock Options
Weighted-average remaining contractual term of stock options outstanding	4 years 2 months 12 days	4 years 4 months 24 days
Weighted-average remaining contractual term of stock options vested and exercisable	3 years 8 months 12 days
Aggregate intrinsic value of stock options outstanding	$ 681,292	$ 740,387
Aggregate intrinsic value of stock options outstanding, vested and exercisable	$ 454,105