Equity Financings (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended	12 Months Ended
	Apr. 03, 2020	Mar. 11, 2020	Oct. 05, 2018	Aug. 27, 2018	Mar. 31, 2020	Dec. 31, 2019
Equity Offerings
Net proceeds					$ 130,754
Underwriters discount and offering costs					8,100
Underwriter's option
Equity Offerings
Issuance of common stock	979,371	2,400,000
Period granted		30 days
Price per share	$ 7.89
Net proceeds	$ 7,200
Shelf
Equity Offerings
Share authorized value (shelf)	$ 18,300				$ 26,100
Registration period				3 years
Sales agreement			$ 50,000
Shelf | Maximum
Equity Offerings
Additional authorized value of securities				$ 250,000
2020 Offering
Equity Offerings
Issuance of common stock	16,979,371	16,000,000
Price per share		$ 7.89
Net proceeds	$ 125,400	$ 118,200
ATM
Equity Offerings
Issuance of common stock					2,352,671	2,592,934
Net proceeds					$ 12,500	$ 13,100