Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies (Income Taxes) (Details)

v3.20.4
Summary of Significant Accounting Policies (Income Taxes) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Tax Disclosure [Line Items]      
Approximate amount by which basis of assets and liabilities for tax reporting purposes is higher (lower) than amount reported on consolidated balance sheet $ 10    
Common Shares      
Income Tax Disclosure [Line Items]      
Ordinary income 45.10% 54.40% 83.10%
Long-term capital gain 54.90% 45.60% 0.00%
Return of capital 0.00% 0.00% 16.90%