Reportable Segments - Reconciliation of NOI from Rental Real Estate Specific to Continuing Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Rental income	$ 2,571,705	$ 2,700,691	$ 2,577,681
Property and maintenance expense	(440,998)	(446,845)	(429,335)
Real estate taxes and insurance expense	(381,562)	(366,139)	(357,814)
Operating income	1,317,990	1,356,160	1,114,617
Same Store, Non-same Store and Other
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Rental income	2,571,705	2,700,691	2,577,681
Property and maintenance expense	(440,998)	(446,845)	(429,335)
Real estate taxes and insurance expense	(381,562)	(366,139)	(357,814)
Total operating expenses	(822,560)	(812,984)	(787,149)
Operating income	$ 1,749,145	$ 1,887,707	$ 1,790,532