Shareholders' Equity/Partners' Capital (Preferred shares of beneficial interest) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Details Of Preferred Shares Of Beneficial Interest
Dividends on preferred shares / Distributions to preferred unitholders (see Note 11 for dividends per share amounts)	$ 62,116	$ 65,880	$ 51,739
Preferred shares of beneficial interest: authorized shares (shares)	110,000,000	110,000,000
Preferred stock, value, issued , balance	$ 1,182,459	$ 1,182,459
Preferred shares/units of beneficial interest: outstanding shares (shares)	48,792,902	48,792,902
6.5% Series A | Convertible Preferred Stock
Details Of Preferred Shares Of Beneficial Interest
Preferred stock dividend rate	6.50%	6.50%
Preferred shares of beneficial interest: authorized shares (shares)	12,902	12,902
Preferred stock, value, issued , balance	$ 920	$ 920
Preferred shares/units of beneficial interest: outstanding shares (shares)	12,902	12,902
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 50.00	$ 50.00
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	3.25	3.25
Preferred stock, redemption price per share (in common shares/Class A units per share/unit)	1.9531	1.9531
6.5% Series A | Convertible Preferred Stock | Class A Unit
Details Of Preferred Shares Of Beneficial Interest
Preferred stock, redemption price per share (in common shares/Class A units per share/unit)	$ 1.9531	$ 1.9531
5.40% Series L | Redeemable Preferred Stock
Details Of Preferred Shares Of Beneficial Interest
Preferred stock dividend rate	5.40%	5.40%
Preferred shares of beneficial interest: authorized shares (shares)	13,800,000	13,800,000
Preferred stock, value, issued , balance	$ 290,306	$ 290,306
Preferred shares/units of beneficial interest: outstanding shares (shares)	12,000,000	12,000,000
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 25.00	$ 25.00
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 1.35	$ 1.35
5.25% Series M | Redeemable Preferred Stock
Details Of Preferred Shares Of Beneficial Interest
Preferred stock dividend rate	5.25%	5.25%
Preferred shares of beneficial interest: authorized shares (shares)	13,800,000	13,800,000
Preferred stock, value, issued , balance	$ 308,946	$ 308,946
Preferred shares/units of beneficial interest: outstanding shares (shares)	12,780,000	12,780,000
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 25.00	$ 25.00
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 1.3125	$ 1.3125
5.25% Series N | Redeemable Preferred Stock
Details Of Preferred Shares Of Beneficial Interest
Preferred stock dividend rate	5.25%	5.25%
Preferred shares of beneficial interest: authorized shares (shares)	12,000,000	12,000,000
Preferred stock, value, issued , balance	$ 291,134	$ 291,134
Preferred shares/units of beneficial interest: outstanding shares (shares)	12,000,000	12,000,000
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 25.00	$ 25.00
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 1.3125	$ 1.3125
4.45% Series O | Redeemable Preferred Stock
Details Of Preferred Shares Of Beneficial Interest
Preferred stock dividend rate	4.45%	4.45%
Preferred shares of beneficial interest: authorized shares (shares)	12,000,000	12,000,000
Preferred stock, value, issued , balance	$ 291,153	$ 291,153
Preferred shares/units of beneficial interest: outstanding shares (shares)	12,000,000	12,000,000
Preferred stock, liquidation preference per share (in dollars per share/unit)	$ 25.00	$ 25.00
Preferred stock, dividend rate, per-dollar-amount (in dollars per share)	$ 1.1125	$ 1.1125