Income Taxes - Schedule of Per Share Distributions to Stockholders (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Common share distribution	$ 0.990000	$ 0.950000	$ 0.900000
Ordinary income	0.438792	0.655535	0.619368
Capital gains	0.551208	0.021022	0.102552
Unrecaptured Sec. 1250 gain	0.132280	0.004647	0.045432
Section 19A Dividends	$ 0.438792
Return of capital		$ 0.273443	$ 0.178080