Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$ 3,951,719	$ 3,830,824	$ 3,658,438
Additions:
Acquisitions	0	509,654	62,587
Capital expenditures and assets placed into service	145,378	129,274	356,857
Less:
Dispositions/impairments/placed into redevelopment	(50,792)	(469,517)	(189,472)
Retirements	(39,846)	(48,516)	(57,586)
Balance at the end of the year	4,006,459	3,951,719	3,830,824
Operating properties	4,006,459	3,951,719	3,830,824
Tax basis of assets, cost for income tax purposes	3,200,000	3,300,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	885,407	913,297	885,392
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense	144,131	137,213	154,029
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions/impairments/placed into redevelopment	(16,783)	(117,589)	(74,178)
Retirements	(39,437)	(47,514)	(51,946)
Balance at the end of the year	973,318	885,407	913,297
Per consolidated balance sheet	$ 973,318	$ 885,407	$ 913,297
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