Schedule III-Real Estate and Accumulated Depreciation - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in total real estate assets
Balances, beginning of year	$ 8,878,820	$ 9,127,533	$ 9,209,211
Additions	176,690	246,719	202,280
Dispositions and retirements	(62,461)	(495,432)	(283,958)
Balances, end of year	8,993,049	8,878,820	9,127,533
Aggregate gross cost of the property for federal income tax purposes	8,446,407
Changes in accumulated depreciation
Balances, beginning of year	2,093,044	2,018,303	1,851,901
Additions	287,846	275,236	277,917
Dispositions and retirements	(31,354)	(200,495)	(111,515)
Balances, end of year	$ 2,349,536	$ 2,093,044	$ 2,018,303
Buildings and improvements | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	5 years
Buildings and improvements | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	40 years
Tenant improvements | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	5 years
Tenant improvements | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	7 years
Equipment and furnishings | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	5 years
Equipment and furnishings | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	7 years