Reportable Segments (Reconciliation of Net Income to Net Operating Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Net Income	$ 80,104	$ 125,629	$ 53,008
Net operating income from unconsolidated joint ventures	28,785	24,335	25,897
Net operating income from discontinued operations	78,591	103,198	102,616
Fee income	(8,347)	(7,297)	(12,519)
Other income	(1,050)	(828)	(919)
Reimbursed expenses	3,259	3,430	3,652
General and administrative expenses	25,592	16,918	19,784
Total interest expense	26,650	22,735	20,983
Depreciation and amortization	97,948	71,625	62,258
Acquisition and merger costs	24,521	299	1,130
Other	5,888	1,181	3,729
Loss on extinguishment of debt	5,180	0	0
Benefit for income taxes from operations	0	0	(20)
Income from unconsolidated joint ventures	(10,562)	(8,302)	(11,268)
Gain on sale of investment properties	(77,114)	(80,394)	(12,536)
Income (loss) from discontinued operations	(19,163)	(31,297)	(40,122)
Net Operating Income	$ 260,282	$ 241,232	$ 215,673