Combined Guarantor Subsidiiaries - Combined Statements of Cash Flows - Summary (Details) - USD ($) $ in Thousands		3 Months Ended							6 Months Ended	9 Months Ended			12 Months Ended
		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018		Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss		$ (92,034)				$ (2,971)				$ (168,531)		$ (33,608)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization										198,438		217,261
Net amortization of deferred financing costs, debt premiums and discounts										6,328		5,451
Net amortization of intangible lease assets and liabilities										(1,212)		198
Gain on sales of real estate assets										(13,811)		(15,998)
Gain on insurance proceeds										(421)		0
Write-off of development projects										41		377
Loss on impairment		135,688				14,600				202,121		84,644
Gain on extinguishment of debt										(71,722)		0
Change in estimate of uncollectable rental revenues										1,504		3,273
Changes in:
Tenant and other receivables										(2,926)		3,493
Other assets										(5,541)		(4,640)
Accounts payable and accrued liabilities										75,071		16,034
Net cash provided by operating activities										225,243		280,407
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to real estate assets										(90,436)		(107,981)
Acquisitions of real estate assets										0		(3,301)
Proceeds from sales of real estate assets										128,364		70,419
Proceeds from insurance										740		0
Payments received on mortgage and other notes receivable										1,853		775
Changes in other assets										(2,497)		(5,903)
Net cash provided by (used in) investing activities										55,870		(14,325)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on mortgage and other indebtedness										(1,232,480)		(649,904)
Net cash used in financing activities										(275,369)		(278,109)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH										5,744		(12,027)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, beginning of period					$ 57,512			$ 68,172	$ 68,172	57,512		68,172	$ 68,172
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, end of period		63,256				56,145				63,256		56,145	57,512
Reconciliation from condensed consolidated statements of cash flows to condensed consolidated balance sheets:
Cash and cash equivalents		34,565	[1]			20,695				34,565	[1]	20,695	25,138	[1]
Restricted cash
Restricted cash	[2]														$ 180		$ 4,681
Mortgage escrows	[2]														28,511		30,769
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, end of period		63,256			57,512	56,145		68,172	68,172	57,512		68,172	57,512		63,256	$ 57,512	56,145
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized										136,117		136,301
Guarantor Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss		21,036		$ 22,775	62,109	27,094	$ 27,117	29,615		105,920		83,826
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization										71,499		73,587
Net amortization of deferred financing costs, debt premiums and discounts										186		3
Net amortization of intangible lease assets and liabilities										(1,224)		(2,539)
Gain on sales of real estate assets									(698)	(20)		(2,406)
Gain on insurance proceeds										(9)		0
Write-off of development projects										0		228
Loss on impairment		0				0				22,770		0
Gain on extinguishment of debt										(61,796)		0
Change in estimate of uncollectable rental revenues										1,262		1,154
Changes in:
Tenant and other receivables										(1,923)		395
Other assets										(1,924)		(1,830)
Accounts payable and accrued liabilities										(3,160)		(582)
Net cash provided by operating activities										131,581		151,836
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to real estate assets										(26,475)		(33,302)
Acquisitions of real estate assets										0		(3,301)
Proceeds from sales of real estate assets										22		3,453
Proceeds from insurance										653		0
Payments received on mortgage and other notes receivable										12,744		65,412
Changes in other assets										(1,263)		(1,031)
Net cash provided by (used in) investing activities										(14,319)		31,231
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on mortgage and other indebtedness										(11,138)		(43,361)
Distributions to owners										(163,113)		(223,696)
Contributions from owners										57,892		79,355
Net cash used in financing activities										(116,359)		(187,702)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH										903		(4,635)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, beginning of period					13,020			14,544	14,544	13,020		14,544	14,544
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, end of period		13,923				9,909				13,923		9,909	13,020
Reconciliation from condensed consolidated statements of cash flows to condensed consolidated balance sheets:
Cash and cash equivalents		9,796				2,954				9,796		2,954	5,880
Restricted cash
Restricted cash															0		3,773
Mortgage escrows															4,127	7,139	3,182
CASH, CASH EQUIVALENTS AND RESTRICTED CASH, end of period		$ 13,923			$ 13,020	$ 9,909		$ 14,544	$ 14,544	13,020		14,544	$ 13,020		$ 13,923	$ 13,020	$ 9,909
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized										$ 10,099		$ 15,167

[1] As of September 30, 2019, includes $484,345 of assets related to consolidated variable interest entities that can be used only to settle obligations of the consolidated variable interest entities and $346,999 of liabilities of consolidated variable interest entities for which creditors do not have recourse to the general credit of the Company. See Note 7.

[2] Included in intangible lease assets and other assets in the condensed consolidated balance sheets.