Reportable Segments (Reconciliation of Net Income to Net Operating Income) (Details) - USD ($)	2 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting [Abstract]
Net Operating Income		$ 80,115,000	$ 59,008,000	$ 160,281,000	$ 118,521,000
Net operating income from unconsolidated joint ventures		(7,609,000)	(6,954,000)	(16,783,000)	(13,600,000)
Net operating income from discontinued operations		0	(25,126,000)	0	(50,444,000)
Fee income		1,854,000	1,824,000	3,791,000	4,023,000
Other income		3,174,000	27,000	8,600,000	417,000
Reimbursed expenses		(907,000)	(798,000)	(1,772,000)	(1,668,000)
General and administrative expenses		(8,618,000)	(4,691,000)	(14,828,000)	(12,934,000)
Interest expense		(8,523,000)	(5,369,000)	(18,264,000)	(10,808,000)
Depreciation and amortization		(50,040,000)	(16,641,000)	(104,924,000)	(33,182,000)
Acquisition and transaction costs		(246,000)	(2,424,000)	(2,177,000)	(2,443,000)
Gain on extinguishment of debt	$ 2,200,000	1,829,000	0	1,829,000	0
Other expenses		(236,000)	(152,000)	(612,000)	(507,000)
Income from unconsolidated joint ventures		40,320,000	1,784,000	40,901,000	3,618,000
Gain (loss) on sale of investment properties		119,832,000	(246,000)	119,761,000	13,944,000
Income from discontinued operations		0	7,523,000	0	15,624,000
Net income		$ 170,945,000	$ 7,765,000	$ 175,803,000	$ 30,561,000