Stockholders Equity - RSU activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Weighted-average grant date fair value (per share)
Stock-based compensation					$ 5,400	$ 1,500
Non-cash compensation expense not yet charged to net income					$ 13,700	$ 15,700
RSAs | Certain employees
Number of shares
Outstanding, Beginning balance	1,129,649	1,141,309	1,157,761	1,009,617	1,009,617
Granted (in shares)		17,200		208,514
Vested (in shares)	(254,521)	(26,602)	(16,452)	(60,370)
Forfeited (in shares)		(2,258)
Canceled (in shares)	(3,049)				(3,049)
Outstanding, Ending balance	872,079	1,129,649	1,141,309	1,157,761	872,079	1,009,617
Grant date fair value
Beginning balance	$ 17,743	$ 17,900	$ 18,126	$ 15,722	$ 15,722
Granted		200		3,298
Vested	(3,958)	(320)	(227)	(894)
Forfeited		(37)
Canceled	(48)
Ending balance	$ 13,737	$ 17,743	$ 17,900	$ 18,126	$ 13,737	$ 15,722
Weighted-average grant date fair value (per share)
Beginning balance	$ 15.71	$ 15.68	$ 15.66	$ 15.57	$ 15.57
Granted (in per share)		11.63		15.82
Vested (in per share)	15.55	12.03	13.78	14.81
Forfeited (in per share)		16.26
Canceled (in per share)	15.86
Ending balance	$ 15.75	$ 15.71	$ 15.68	$ 15.66	$ 15.75	$ 15.57