Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal income tax expense	$ (9,912,000)	$ 1,083,000	$ 420,000
Net tax benefit due to Tax Act	3,900,000
Net operating loss carryforward	6,200,000
Cost of real estate for federal income tax purposes	3,500,000,000
Net deferred tax liability	$ 8,202,000	$ 0
Dividends declared (in dollars per share)	$ 0.45	$ 0	$ 0
Dividends declared, taxable in current year (in dollars per share)	0.31
Dividends declared, taxable in next fiscal year (in dollars per share)	$ 0.14
REIT Subsidiaries
Income Taxes [Line Items]
Federal income tax expense	$ 0	$ 0	$ 0