Stock-Based Compensation - Summary of Stock Options (Details) - Options to purchase common stock $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) $ / shares shares
Shares
Options outstanding at beginning of period (in shares) | shares	5,463
Granted (in shares) | shares	1,044
Exercised (in shares) | shares	(341)
Canceled (in shares) | shares	(499)
Expired (in shares) | shares	(806)
Options outstanding at end of period (in shares) | shares	4,861
Options exercisable at end of period (in shares) | shares	2,810
Weighted- Average Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 36.88
Granted (in dollars per share) | $ / shares	19.72
Exercised (in dollars per share) | $ / shares	8.40
Canceled (in dollars per share) | $ / shares	33.99
Expired (in dollars per share) | $ / shares	40.15
Options outstanding at the end of the period (in dollars per share) | $ / shares	34.94
Options exercisable at the end of the period (in dollars per share) | $ / shares	$ 39.87
Weighted- Average Contractual Life (in years)
Options outstanding at the end of period	7 years 4 months 20 days
Options exercisable at the end of period	6 years 4 months 24 days
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars) | $	$ 11,716
Options exercisable at the end of the period (in dollars) | $	$ 4,900