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						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic earnings per share:
Net earnings (losses)	$ 1,546	$ 4,709	$ 2,808	$ 3,073	$ 3,503	$ (11,427)	$ 9,063	$ (4,851)
Basic weighted average number of shares outstanding (in shares)	4,274			4,242			4,258	4,239
Basic earnings (losses) per share (in dollars per share)	$ 0.36			$ 0.72			$ 2.13	$ (1.14)
Diluted weighted average number of shares outstanding:
Common shares (in shares)	4,274			4,242			4,258	4,239
Total diluted shares (in shares)	4,297			4,253			4,280	4,239
Diluted earnings (losses) per share (in dollars per share)	$ 0.36			$ 0.72			$ 2.12	$ (1.14)
Restricted stock units awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	17			9			16	0
Performance share unit awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	6			2			6	0