Income Taxes - Schedule of components of distributions made to common stockholders on a per share basis (Details) - $ / shares			12 Months Ended
	Nov. 12, 2015	Oct. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends, dollars per share
Ordinary income (in dollars per share)			$ 1.98	$ 0.94	$ 1.20
Capital gains (in dollars per share)			0.51	3.24	3.64
Unrecaptured Section 1250 gain (in dollars per share)			0.38	0.36	0.00
Return of capital (in dollars per share)			0.00	0.00	0.00
Dividends paid for income tax purposes (in dollars per share)			$ 2.87	$ 4.54	$ 4.84
Dividends, percent
Ordinary income (as a percent)			69.00%	20.80%	24.80%
Capital gains (as a percent)			17.80%	71.40%	75.20%
Unrecaptured Section 1250 gain (as a percent)			13.20%	7.80%	0.00%
Return of capital (as a percent)			0.00%	0.00%	0.00%
Dividends paid (as a percent)			100.00%	100.00%	100.00%
Distributions paid, per share (in dollars per share)					$ 4.63
Dividends declared for common stock (in dollars per share)	$ 2.00	$ 2.00	$ 2.87	$ 2.75	6.63
Cash deemed paid (in dollars per share)					$ 0.21