Income Taxes - Schedule of components of distributions made to common stockholders on a per share basis (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends, dollars per share
Ordinary income (in dollars per share)	$ 1.32	$ 1.91	$ 1.98
Capital gains (in dollars per share)	0.64	0.05	0.51
Unrecaptured Section 1250 gain (in dollars per share)	0	0	0.38
Return of capital (in dollars per share)	1.04	1.01	0
Dividends paid for income tax purposes (in dollars per share)	$ 3.00	$ 2.97	$ 2.87
Dividends, percent
Ordinary income (as a percent)	44.20%	64.30%	69.00%
Capital gains (as a percent)	21.20%	1.70%	17.80%
Unrecaptured Section 1250 gain (as a percent)	0.00%	0.00%	13.20%
Return of capital (as a percent)	34.60%	34.00%	0.00%
Dividends paid (as a percent)	100.00%	100.00%	100.00%