Income Taxes - Income tax expense (benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020
Current:
Federal									$ 969	$ (4,440)
State										6
Total current									969	(4,434)
Deferred:
Federal									1,447	3,008
State									179	207
Total deferred									1,626	3,215
Income tax expense (benefit)	$ 884	$ 1,190	$ 92	$ 429	$ (1,746)	$ 229	$ 92	$ 206	$ 2,595	$ (1,219)