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
	Mar. 31, 2021	Mar. 31, 2020
Basic earnings per share:
Net earnings (losses)	$ 2,808	$ (11,427)
Basic weighted average number of shares outstanding (in shares)	4,246	4,236
Basic earnings (losses) per share (in dollars per share)	$ 0.66	$ (2.70)
Diluted weighted average number of shares outstanding:
Common shares (in shares)	4,246	4,236
Total diluted shares (in shares)	4,271	4,250
Diluted earnings (losses) per share (in dollars per share)	$ 0.66	$ (2.69)
Restricted stock units awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	18	12
Performance share unit awards
Diluted weighted average number of shares outstanding:
Unit awards (in shares)	7	2