Income Taxes - Distributions (Details) - $ / shares					1 Months Ended	12 Months Ended
	Dec. 15, 2020	Dec. 16, 2019	Dec. 14, 2018	Dec. 15, 2017	Dec. 14, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Shares
Real Estate Investment Trust Distributions [Line Items]
Ordinary non-qualified income (in usd per share)						$ 0	$ 0.5609	$ 1.2040
Ordinary non-qualified income, percent						0.00%	30.03%	77.57%
Qualified dividend (in usd per share)						$ 0	$ 0.0069	$ 0.3482
Qualified dividend, percent						0.00%	0.37%	22.43%
Capital gain (in usd per share)						$ 0.0100	$ 1.3000	$ 0
Capital gain, percent						33.33%	69.60%	0.00%
Return of capital (in usd per share)						$ 0.0200	$ 0	$ 0
Return of capital, percent						66.67%	0.00%	0.00%
Total (in usd per share)						$ 0.0300	$ 1.8678	$ 1.5522
Total, percent						100.00%	100.00%	100.00%
Distributions declared, treated as distributions for taxes in next year (in usd per share)	$ 0.0100			$ 0.3800	$ 0.3478
Distributions declared, treated as distributions for taxes in prior year (in usd per share)		$ 0.3800
Series C Cumulative Redeemable Preferred Shares
Real Estate Investment Trust Distributions [Line Items]
Ordinary non-qualified income (in usd per share)						$ 0	$ 0.6100	$ 1.2605
Ordinary non-qualified income, percent						0.00%	30.03%	77.57%
Qualified dividend (in usd per share)						$ 0	$ 0.0075	$ 0.3645
Qualified dividend, percent						0.00%	0.37%	22.43%
Capital gain (in usd per share)						$ 0.4063	$ 1.4138	$ 0
Capital gain, percent						33.34%	69.60%	0.00%
Return of capital (in usd per share)						$ 0.8125	$ 0	$ 0
Return of capital, percent						66.66%	0.00%	0.00%
Total (in usd per share)						$ 1.2188	$ 2.0313	$ 1.6250
Total, percent						100.00%	100.00%	100.00%
Distributions declared, treated as distributions for taxes in next year (in usd per share)			$ 0.4063
Series D Cumulative Redeemable Preferred Shares
Real Estate Investment Trust Distributions [Line Items]
Ordinary non-qualified income (in usd per share)						$ 0	$ 0.5982	$ 1.2363
Ordinary non-qualified income, percent						0.00%	30.03%	77.57%
Qualified dividend (in usd per share)						$ 0	$ 0.0074	$ 0.3575
Qualified dividend, percent						0.00%	0.37%	22.43%
Capital gain (in usd per share)						$ 0.3984	$ 1.3866	$ 0
Capital gain, percent						33.33%	69.60%	0.00%
Return of capital (in usd per share)						$ 0.7969	$ 0	$ 0
Return of capital, percent						66.67%	0.00%	0.00%
Total (in usd per share)						$ 1.1953	$ 1.9922	$ 1.5938
Total, percent						100.00%	100.00%	100.00%
Distributions declared, treated as distributions for taxes in next year (in usd per share)			0.3984
Series E Cumulative Redeemable Preferred Shares
Real Estate Investment Trust Distributions [Line Items]
Ordinary non-qualified income (in usd per share)						$ 0	$ 0.5982	$ 0
Ordinary non-qualified income, percent						0.00%	30.03%	0.00%
Qualified dividend (in usd per share)						$ 0	$ 0.0074	$ 0
Qualified dividend, percent						0.00%	0.37%	0.00%
Capital gain (in usd per share)						$ 0.3984	$ 1.3866	$ 0
Capital gain, percent						33.33%	69.60%	0.00%
Return of capital (in usd per share)						$ 0.7969	$ 0	$ 0
Return of capital, percent						66.67%	0.00%	0.00%
Total (in usd per share)						$ 1.1953	$ 1.9922	$ 0
Total, percent						100.00%	100.00%	0.00%
Distributions declared, treated as distributions for taxes in next year (in usd per share)			0.3984
Series F Cumulative Redeemable Preferred Shares
Real Estate Investment Trust Distributions [Line Items]
Ordinary non-qualified income (in usd per share)						$ 0	$ 0.5912	$ 0
Ordinary non-qualified income, percent						0.00%	30.03%	0.00%
Qualified dividend (in usd per share)						$ 0	$ 0.0073	$ 0
Qualified dividend, percent						0.00%	0.37%	0.00%
Capital gain (in usd per share)						$ 0.3938	$ 1.3703	$ 0
Capital gain, percent						33.34%	69.60%	0.00%
Return of capital (in usd per share)						$ 0.7875	$ 0	$ 0
Return of capital, percent						66.66%	0.00%	0.00%
Total (in usd per share)						$ 1.1813	$ 1.9688	$ 0
Total, percent						100.00%	100.00%	0.00%
Distributions declared, treated as distributions for taxes in next year (in usd per share)			$ 0.3938