Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Income from continuing operations	$ 15,003	$ 20,299	$ 46,670	$ 62,626
Loss from discontinued operations (see Note 8)	0	0	(23,797)	0
Net income	$ 15,003	$ 20,299	$ 22,873	$ 62,626
Weighted average shares outstanding - basic and diluted	5,117,347	5,115,982	5,116,667	5,115,339
Income from continuing operations - basic and diluted (in usd per share)	$ 2.93	$ 3.97	$ 9.12	$ 12.24
Loss from discontinuing operations (see Note 8) - basic and diluted (in usd per share)	0.00	0.00	(4.65)	0.00
Net income per common share - basic and diluted (in usd per share)	$ 2.93	$ 3.97	$ 4.47	$ 12.24

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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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Amount after tax of income (loss) from continuing operations attributable to the parent.

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The amount of net income (loss) from continuing operations per each basic and diluted share of common stock or unit when the per share amount is the same for both basic and diluted shares.

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Amount after tax of income (loss) from a discontinued operation attributable to the parent. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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Per basic and diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation, when the per share amount is the same.

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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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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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