Reportable Segments - Reconciliation of Net Income to Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Net Operating Income	$ 124,148	$ 120,016	$ 369,977	$ 364,930
Net operating income from unconsolidated joint ventures	(5,762)	(4,208)	(15,953)	(14,436)
Total Revenues	188,732	183,380	564,919	557,193
Reimbursed expenses	(383)	(373)	(1,149)	(1,216)
General and administrative expenses	(7,968)	(5,658)	(22,014)	(19,853)
Interest expense	(16,709)	(15,058)	(50,573)	(44,955)
Depreciation and amortization	(72,073)	(71,498)	(214,399)	(215,980)
Transaction costs	0	0	0	(428)
Other expenses	(421)	(723)	(1,835)	(1,841)
Income from unconsolidated joint ventures	2,128	1,611	5,826	6,751
Gain (loss) on sales of investments in unconsolidated joint ventures	13,121	(59)	13,160	45,940
Gain (loss) on investment property transactions	13,063	(523)	13,037	90,192
Net income	54,136	28,255	111,507	226,800
Fee income
Segment Reporting Information [Line Items]
Total Revenues	3,094	4,350	12,426	13,772
Termination fee income
Segment Reporting Information [Line Items]
Total Revenues	1,775	372	2,599	3,755
Other
Segment Reporting Information [Line Items]
Total Revenues	$ 123	$ 6	$ 405	$ 169