Share-Based Compensation - Restricted Stock Units (Details) - Restricted stock units $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Number of shares
Outstanding, beginning balance | shares	826
Granted | shares	431
Released | shares	(345)
Cancelled/Forfeited | shares	(37)
Outstanding, ending balance | shares	875
Vested and expected to vest | shares	875
Weighted Average Share Price on Date of Release	$ 12.68
Weighted Average Fair Value
Outstanding, beginning balance	32.07
Granted	13.42
Released	26.69
Cancelled/Forfeited	26.64
Outstanding, ending balance	25.22
Vested and expected to vest	$ 25.22
Aggregate Intrinsic Value [Abstract]
Aggregate intrinsic value, outstanding | $	$ 12,744
Granted | $	5,787
Released | $	4,378
Cancelled/Forfeited | $	415
Aggregate intrinsic value, outstanding | $	9,819
Vested and expected to vest | $	$ 9,819