Subsequent Event - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	[1]	Dec. 31, 2017	[2]	Jun. 30, 2019	Jan. 31, 2019	Jun. 30, 2018
Subsequent Event [Line Items]
Public offering stock price (USD per share)							$ 97.00	$ 62.00	$ 38.85
Proceeds from issuance of common stock		$ 327,830	$ 130,663		$ 153,530
Common Stock | Subsequent Event
Subsequent Event [Line Items]
Issuance of common stock, net of costs (shares)	3,538,462
Public offering stock price (USD per share)	$ 97.50
Proceeds from issuance of common stock	$ 324,100

[1] Proceeds in 2018 include warrants to purchase up to 421,650 shares of the Company's common stock at a public offering price of $38.849 per warrant, net of issuance costs.

[2] Proceeds in 2017 include warrants to purchase up to 4,137,999 shares of the Company's common stock at a public offering price of $12.999 per warrant, net of issuance costs, and warrants to purchase up to 7,258,263 shares of the Company's common stock at a public offering price of $5.599 per warrant, net of issuance costs.