Equity Incentive Plan - Stock option awards (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Stock option awards
Exercised (shares)		(18)
Stock option awards
Stock option awards
Outstanding as of the beginning of period (shares)	340
Exercised (shares)	0
Expired or canceled (shares)	0
Forfeited (shares)	0
Outstanding as of the end of period (shares)	340		340
Vested and exercisable as of the end of period (shares)	330
Expected to vest as of the end of period (shares)	10
Weighted-average exercise price (per option)
Outstanding as of the beginning of period (USD per share)	$ 12.56
Exercised (USD per share)	0
Expired or canceled (USD per share)	0
Forfeited (USD per share)	0
Outstanding as of the end of period (USD per share)	12.56		$ 12.56
Vested and exercisable as of the end of period (USD per share)	12.51
Expected to vest as of the end of period (USD per share)	$ 14.12
Weighted-average remaining contractual term (years)
Outstanding, weighted-average remaining contractual term	4 years 8 months 15 days		5 years
Vested and exercisable as of the end of period	4 years 7 months 20 days
Expected to vest as of the end of period (in dollars per share)	6 years 10 months 20 days
Vested and exercisable, aggregate intrinsic value	$ 0
Expected to vest, aggregate intrinsic value	0
Stock-based compensation, not yet recognized, stock options	$ 100,000
Recognition period for costs not yet recognized	11 months 1 day