Share-Based Compensation - Restricted Stock Units (Details) - Restricted stock units $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Number of shares
Outstanding, beginning balance | shares	707
Granted | shares	499
Released | shares	(77)
Cancelled/Forfeited | shares	(14)
Outstanding, ending balance | shares	1,115
Exercisable, ending balance | shares	6
Vested and expected to vest | shares	1,115
Weighted Average Share Price on Date of Release | $ / shares	$ 33.72
Weighted Average Fair Value
Outstanding, beginning balance | $ / shares	29.23
Granted | $ / shares	33.42
Released | $ / shares	25.86
Cancelled/Forfeited | $ / shares	32.78
Outstanding, ending balance | $ / shares	$ 31.29
Aggregate Intrinsic Value [Abstract]
Aggregate intrinsic value, outstanding | $	$ 26,732
Granted | $	16,685
Released | $	2,596
Cancelled/Forfeited | $	355
Aggregate intrinsic value, outstanding | $	27,940
Exercisable, ending balance | $	141
Vested and expected to vest | $	$ 27,940