Reportable Segments - Reconciliation of Net Income to Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net Operating Income	$ 122,705	$ 117,132	$ 245,829	$ 244,914
Net operating income from unconsolidated joint ventures	(5,437)	(4,193)	(10,191)	(10,228)
Total Revenues	186,637	179,915	376,187	373,813
Reimbursed expenses	(398)	(322)	(766)	(843)
General and administrative expenses	(7,313)	(8,543)	(14,046)	(14,195)
Interest expense	(16,656)	(13,993)	(33,864)	(29,897)
Depreciation and amortization	(71,456)	(72,868)	(142,326)	(144,482)
Transaction costs	0	(63)	0	(428)
Other expenses	(824)	(552)	(1,414)	(1,118)
Income from unconsolidated joint ventures	1,795	1,715	3,698	5,140
Gain (loss) on sales of investments in unconsolidated joint ventures	0	(231)	39	45,999
Gain (loss) on investment property transactions	(9)	(201)	(26)	90,715
Net income	28,060	23,236	57,371	198,545
Fee income
Segment Reporting Information [Line Items]
Total Revenues	4,803	4,690	9,332	9,422
Termination fee income
Segment Reporting Information [Line Items]
Total Revenues	782	539	824	3,383
Other
Segment Reporting Information [Line Items]
Total Revenues	$ 68	$ 126	$ 282	$ 163