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, 2019	Mar. 31, 2018
Basic earnings per share:
Net earnings	$ 4,908	$ 1,138
Basic weighted average number of shares outstanding (in shares)	4,218	4,218
Basic earnings per share (in dollars per share)	$ 1.16	$ 0.27
Diluted earnings per share:
Basic weighted average number of shares outstanding (in shares)	4,218	4,218
Total (in shares)	4,224	4,218
Diluted earnings per share (in dollars per share)	$ 1.16	$ 0.27
Restricted stock unit awards
Diluted earnings per share:
Unit awards	6	0
Performance Unit Awards
Diluted earnings per share:
Unit awards	0	0

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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