Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Income from continuing operations	$ 17,570	$ 20,660	$ 31,667	$ 42,327
Loss from discontinued operations (see Note 8)	0	0	(23,797)	0
Net income	$ 17,570	$ 20,660	$ 7,870	$ 42,327
Weighted average shares outstanding - basic and diluted	5,116,657	5,115,320	5,116,321	5,115,012
Income from continuing operations - basic and diluted (in usd per share)	$ 3.43	$ 4.04	$ 6.19	$ 8.28
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)	$ 3.43	$ 4.04	$ 1.54	$ 8.28