Reportable Segments (Reconciliation of Net Income to Net Operating Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Net income	$ 219,959	$ 80,104	$ 125,629
Net operating income from unconsolidated joint ventures	31,053	28,785	24,335
Net operating income from discontinued operations	0	78,591	103,198
Fee income	(8,632)	(8,347)	(7,297)
Other income	(11,518)	(1,050)	(828)
Reimbursed expenses	3,527	3,259	3,430
General and administrative expenses	27,523	25,592	16,918
Total interest expense	33,524	26,650	22,735
Depreciation and amortization	196,745	97,948	71,625
Acquisition and transaction costs	1,661	24,521	299
Other	1,796	5,888	1,181
(Gain) loss on extinguishment of debt	(2,258)	5,180	0
Income from unconsolidated joint ventures	(47,115)	(10,562)	(8,302)
Gain on sale of investment properties	(133,059)	(77,114)	(80,394)
Income from discontinued operations	0	(19,163)	(31,297)
Net Operating Income	$ 313,206	$ 260,282	$ 241,232