Share-Based Compensation - Summary of Stock Option Activity (Details) - Stock options shares in Thousands	9 Months Ended
	Sep. 30, 2020 $ / shares shares
Number of Shares Underlying Options
Outstanding, beginning balance (in shares) | shares	6,780
Granted (in shares) | shares	990
Exercised (in shares) | shares	(73)
Forfeited (in shares) | shares	(264)
Expired (in shares) | shares	(7)
Outstanding, ending balance (in shares) | shares	7,426
Vested and exercisable, end of period (in shares) | shares	3,968
Vested and expected to vest, end of period (in shares) | shares	7,114
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 10.89
Granted (in dollars per share) | $ / shares	4.02
Exercised (in dollars per share) | $ / shares	2.55
Forfeited (in dollars per share) | $ / shares	16.21
Expired (in dollars per share) | $ / shares	1.59
Outstanding, ending balance (in dollars per share) | $ / shares	9.88
Vested and exercisable, end of period (in dollars per share) | $ / shares	15.33
Vested and expected to vest, end of period (in dollars per share) | $ / shares	$ 10.15