Shareholders' Equity/Partners' Capital (Schedule of Dividends) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Class of Stock [Line Items]
Common shares of beneficial interest: authorized shares (shares)	250,000,000		250,000,000
Common shares, dividends (in dollars per share)	$ 0.53	$ 0.53
Preferred shares of beneficial interest: authorized shares (shares)	110,000,000		110,000,000
Common Class A
Class of Stock [Line Items]
Common shares of beneficial interest: authorized shares (shares)	250,000,000	250,000,000
Common shares, dividends (in dollars per share)	$ 0.53	$ 0.53
Series A Preferred Stock | Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)	6.50%	6.50%
Preferred shares of beneficial interest: authorized shares (shares)	12,902	13,402
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 0.8125	$ 0.8125
Preferred stock, redemption price per share (in common shares/Class A units per share/unit)	1.9531	1.9531
Series A Preferred Stock | Convertible Preferred Stock | Class A Unit
Class of Stock [Line Items]
Preferred stock, redemption price per share (in common shares/Class A units per share/unit)	$ 1.9531	$ 1.9531
Series K Preferred Stock | Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)		5.70%
Preferred shares of beneficial interest: authorized shares (shares)		12,000,000
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)		$ 0.3563
Series L Preferred Stock | Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)	5.40%	5.40%
Preferred shares of beneficial interest: authorized shares (shares)	13,800,000	13,800,000
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 0.3375	$ 0.3375
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 25.00	$ 25.00
Series M Preferred Stock | Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)	5.25%	5.25%
Preferred shares of beneficial interest: authorized shares (shares)	13,800,000	13,800,000
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 0.3281	$ 0.3281
Series N Preferred Stock | Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)	5.25%
Preferred shares of beneficial interest: authorized shares (shares)	12,000,000	12,000,000
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 0.3281	$ 0.3281
Series O Preferred Stock | Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage (percent)	4.45%
Preferred shares of beneficial interest: authorized shares (shares)	12,000,000
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 0.2781