Reportable Segments - Reconciliation of NOI from Rental Real Estate Specific to Continuing Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Rental income	$ 2,470,689	$ 2,422,233	$ 2,736,578
Property and maintenance expense	(405,281)	(406,823)	(479,160)
Real estate taxes and insurance expense	(335,495)	(317,387)	(339,802)
Operating income	847,471	856,086	1,009,238
Same Store, Non-same Store and Other
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
Rental income	2,470,689	2,422,233	2,736,578
Property and maintenance expense	(405,281)	(406,823)	(479,160)
Real estate taxes and insurance expense	(335,495)	(317,387)	(339,802)
Total operating expenses	(740,776)	(724,210)	(818,962)
Operating income	$ 1,729,913	$ 1,698,023	$ 1,917,616