Income Taxes - Taxability of Cash Distributions Paid on Common Shares (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Ordinary income		$ 2.55	$ 2.67
Capital gains	$ 0.05	0.05	0.05
Return of capital	1.80	0.88
Total	$ 1.85	$ 3.48	$ 2.72