Basic and Diluted Net Loss Per Share - Potential Shares of Common Stock Excluded from Diluted Weighted-Average Common Shares Outstanding (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	5,968	8,816	6,963	8,733
Shares of common stock issuable under equity incentive awards outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	4,590	6,677	5,000	7,146
Shares of common stock related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from diluted net loss per share (in shares)	1,378	2,139	1,963	1,587