Reportable Segments (Reconciliation of Net Income to Net Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net Operating Income	$ 120,642	$ 80,858	$ 305,790	$ 241,631
Net operating income from unconsolidated joint ventures	(9,037)	(6,994)	(26,289)	(21,643)
Revenues	188,323	118,706	463,076	352,536
Reimbursed expenses	(1,290)	(955)	(3,269)	(2,757)
General and administrative expenses	(5,852)	(3,913)	(25,686)	(18,793)
Interest expense	(14,700)	(9,551)	(37,579)	(29,043)
Depreciation and amortization	(82,012)	(45,068)	(178,777)	(135,836)
Acquisition and transaction costs	(1,048)	0	(50,878)	(228)
Other expenses	(297)	(93)	(1,101)	(457)
Income from unconsolidated joint ventures	3,241	2,252	9,779	10,173
Gain (loss) on sale of investment properties	(27)	(33)	14,388	4,912
Gain on extinguishment of debt	0	93	0	8
Net income	20,692	19,859	34,115	58,014
Fee income
Segment Reporting Information [Line Items]
Revenues	7,494	2,519	23,298	7,211
Termination fee income
Segment Reporting Information [Line Items]
Revenues	3,575	276	4,285	1,275
Other
Segment Reporting Information [Line Items]
Revenues	$ 3	$ 468	$ 154	$ 1,561