Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands			2 Months Ended	12 Months Ended
	Feb. 21, 2020	Feb. 19, 2020	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 12, 2018
Subsequent events
Number of shares issued			283,452
Common stock, par value				$ 0.001	$ 0.001	$ 0.001
Purchase price (in dollar per share)			$ 6.88
Gross and net proceeds from issuance of common stock			$ 1,950	$ 17,810	$ 56,513
Subsequent events
Subsequent events
Number of shares issued	300,000	2,000,000
Purchase price (in dollar per share)	$ 30.08	$ 32.00
Gross and net proceeds from issuance of common stock		$ 64,000
Shares repurchased (in shares)	300,000