Segment Reporting - Reconciliation of Segment Earnings to Earnings Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings	$ 2,960	$ 6,335	$ 11,108	$ 10,186
General and administrative	(4,211)	(2,961)	(8,229)	(6,337)
Interest and other income	303	62	327	196
Interest expense	(136)	(204)	(250)	(424)
Earnings before income taxes	3,127	6,193	11,185	9,958
Operating segments
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings	7,171	9,296	19,337	16,523
General and administrative
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings	0	0	0	0
General and administrative	(4,211)	(2,961)	(8,229)	(6,337)
Segment reconciling items
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Interest and other income	303	62	327	196
Interest expense	$ (136)	$ (204)	$ (250)	$ (424)