Segment Information - Reconciliation of Consolidated Net Income to Consolidated NOI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting [Abstract]
Net income (loss)	$ (43,262)	$ 19,046	$ 14,579	$ 48,015
Plus:
Interest expense	19,257	19,732	58,091	61,473
Interest expense - amortization of deferred financing costs	618	577	1,872	1,807
Depreciation and amortization	43,900	42,429	130,908	132,584
General and administrative expenses	5,963	5,813	22,209	21,797
Equity in (income) loss of Real Estate Ventures	(1)	5,723	1,182	5,387
Provision for impairment	56,865	0	56,865	3,057
Less:
Interest income	1,220	79	2,564	635
Income tax (provision) benefit	0	793	(158)	1,032
Net gain (loss) on disposition of real estate	0	0	(35)	8,411
Net gain on sale of undepreciated real estate	0	953	2,859	953
Net gain on Real Estate Venture transactions	0	13,758	37,263	28,340
Consolidated net operating income	$ 82,120	$ 77,737	$ 243,213	$ 234,749