Basis of Presentation and Significant Accounting Policies - Summary of Characterization of Dividend Distributions for Federal Income Tax Purposes (Details) - $ / shares	1 Months Ended		12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Cash dividend	$ 0.095	$ 0.095	$ 0.395	$ 0.380	$ 0.380
Ordinary income			72.40%	51.30%	28.20%
Long-term capital gain			18.70%	8.90%
Return of capital			8.90%	39.80%	71.80%
Total			100.00%	100.00%	100.00%
Ordinary Income [Member]
Income Taxes [Line Items]
Cash dividend			$ 0.286	$ 0.195	$ 0.107
Long-Term Capital Gain [Member]
Income Taxes [Line Items]
Cash dividend			0.074	0.034
Return of Capital [Member]
Income Taxes [Line Items]
Cash dividend			$ 0.035	$ 0.151	$ 0.273