Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$ 4,006,459	$ 3,951,719	$ 3,830,824
Additions:
Acquisitions	9,722	0	509,654
Capital expenditures and assets placed into service	113,221	145,378	129,274
Less:
Dispositions/impairments/placed into redevelopment	(619,086)	(50,792)	(469,517)
Retirements	(36,207)	(39,846)	(48,516)
Balance at the end of the year	3,474,109	4,006,459	3,951,719
Operating properties	3,474,109	4,006,459	3,951,719
Tax basis of assets, cost for income tax purposes	2,900,000	3,200,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	973,318	885,407	913,297
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense	138,822	144,131	137,213
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions/impairments/placed into redevelopment	(182,526)	(16,783)	(117,589)
Retirements	(33,053)	(39,437)	(47,514)
Balance at the end of the year	896,561	973,318	885,407
Per consolidated balance sheet	$ 896,561	$ 973,318	$ 885,407
Leashold Interest Land
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Lease agreement term	99 years
Maximum
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Useful life	55 years