Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 25, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Net cash paid for income taxes		$ 368,000	$ 341,000	$ 316,000
Percentage of ordinary income		61.60%	83.80%	43.90%
Capital gain distributions percentage		34.40%	16.20%	56.10%
Non-taxable distributions percentage		4.00%	0.00%	0.00%
Percentage of taxable income distributed among stockholders		90.00%
Percentage of common stock to total required distribution		80.00%
Dividend declared date	Nov. 25, 2015
Special dividend declared	$ 0.22	$ 1.03	$ 1.15	$ 0.960
Common Stock issued	255,747
Cash payments to shareholders	$ 2,941,000	$ 36,231,000	$ 35,150,000	$ 28,675,000
Marketing Estate [Member]
Income Tax [Line Items]
Distributions received from settlement of claims			$ 18,177,000
Minimum [Member]
Income Tax [Line Items]
Percentage of dividend to be distributed as cash	20.00%
Maximum [Member]
Income Tax [Line Items]
Percentage of dividend to be distributed as cash	40.00%