Income Taxes - Summary of Average Taxable Nature of Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Stock
Income Tax Contingency [Line Items]
Total dividends per share, common (usd per share)	$ 0.420	$ 0.485	$ 0.710
Taxable percentage allocation on dividends	100.00%	100.00%	100.00%
Common Stock | Ordinary income
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	95.10%	61.07%	87.89%
Common Stock | Qualifying dividend
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	0.60%	0.22%	0.14%
Common Stock | Capital gain
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	0.00%	0.00%	0.00%
Common Stock | Return of capital
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	4.30%	38.71%	11.97%
Series C
Income Tax Contingency [Line Items]
Total dividends per share, preferred (usd per share)	$ 3.25	$ 3.25	$ 3.25
Taxable percentage allocation on dividends	100.00%	100.00%	100.00%
Series C | Ordinary income
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	99.38%	99.64%	99.84%
Series C | Qualifying dividend
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	0.62%	0.36%	0.16%
Series C | Capital gain
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	0.00%	0.00%	0.00%
Series C | Return of capital
Income Tax Contingency [Line Items]
Taxable percentage allocation on dividends	0.00%	0.00%	0.00%