Schedule III-Real Estate and Accumulated Depreciation - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in total real estate assets
Balances, beginning of year	$ 8,993,049	$ 8,878,820	$ 9,127,533
Additions	419,369	176,690	246,719
Dispositions and retirements	(155,706)	(62,461)	(495,432)
Balances, end of year	9,256,712	8,993,049	8,878,820
Aggregate gross cost of the property for federal income tax purposes	9,178,539
Changes in accumulated depreciation
Balances, beginning of year	2,349,536	2,093,044	2,018,303
Additions	287,925	287,846	275,236
Dispositions and retirements	(75,328)	(31,354)	(200,495)
Balances, end of year	$ 2,562,133	$ 2,349,536	$ 2,093,044
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