Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Earnings (Losses) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic earnings per share:
Net earnings (losses)	$ 4,709	$ 2,808	$ 3,503	$ (11,427)	$ 7,517	$ (7,924)
Basic weighted average number of shares outstanding (in shares)	4,254		4,239		4,250	4,237
Basic earnings (losses) per share (in dollars per share)	$ 1.11		$ 0.83		$ 1.77	$ (1.87)
Diluted weighted average number of shares outstanding:
Common shares (in shares)	4,254		4,239		4,250	4,237
Total diluted shares (in shares)	4,273		4,253		4,272	4,237
Diluted earnings (losses) per share (in dollars per share)	$ 1.10		$ 0.82		$ 1.76	$ (1.87)
Restricted stock units awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	13		12		15	0
Performance share unit awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	6		2		7	0