Income Taxes - Schedule of components of distributions made to common stockholders on a per share basis (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Dividends, dollars per share
Ordinary income (in dollars per share)	$ 0.08	$ 1.32	$ 1.91
Capital gains (in dollars per share)	0.02	0.64	0.05
Return of capital (in dollars per share)	1.45	1.04	1.01
Dividends paid for income tax purposes (in dollars per share)	$ 1.55	$ 3.00	$ 2.97
Dividends, percent
Ordinary income (as a percent)	5.20%	44.20%	64.30%
Capital gains (as a percent)	1.30%	21.20%	1.70%
Return of capital (as a percent)	93.50%	34.60%	34.00%
Dividends paid (as a percent)	100.00%	100.00%	100.00%