Equity and EPS - The Computations of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operations:
Net income	$ 11,822	$ 9,008	$ 7,527	$ 8,927	$ 12,639	$ 14,137	$ 6,369	$ 8,678	$ 37,284	$ 41,823	$ 31,184
Less: Income attributable to participating securities (unvested shares and units)									708	996	954
Net income attributable to common shareholders and used in Earnings Per Share calculation (Note 7)									$ 36,576	$ 40,827	$ 30,230
Share information:
Basic and diluted weighted average common shares (in shares)									16,866,176	16,746,731	16,643,811
Basic and diluted EPS (in dollars per share)	$ 0.69	$ 0.52	$ 0.44	$ 0.52	$ 0.74	$ 0.82	$ 0.37	$ 0.50	$ 2.17	$ 2.44	$ 1.82

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or 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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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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