Investments in Unconsolidated Joint Ventures - Combined Condensed Statements of Operations of unconsolidated joint ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Leasing revenue	$ 214,260		$ 636,290
Expenses:
Company's equity in net (loss) income	14,582	$ 18,789	34,082	$ 51,330
Joint Venture
Revenues:
Leasing revenue	215,440	223,849	652,603	670,682
Other	16,316	11,794	42,094	32,544
Total revenues	231,756	235,643	694,697	703,226
Expenses:
Shopping center and operating expenses	67,947	71,421	204,804	212,265
Leasing expenses	2,157		6,359
Interest expense	52,947	54,648	161,534	158,532
Depreciation and amortization	88,943	85,905	280,522	257,845
Total operating expenses	211,994	211,974	653,219	628,642
(Loss) gain on sale or write down of assets, net	5	12,575	(680)	14,104
Net (loss) income	19,767	36,244	40,798	88,688
Company's equity in net (loss) income	14,582	18,789	34,082	51,330
Joint Venture | PPR Portfolio
Revenues:
Leasing revenue	46,308	46,859	137,674	137,641
Other	668	27	1,285	627
Total revenues	46,976	46,886	138,959	138,268
Expenses:
Shopping center and operating expenses	9,289	9,893	27,431	29,091
Leasing expenses	407		1,247
Interest expense	16,926	16,680	50,920	50,176
Depreciation and amortization	25,260	24,582	75,506	73,137
Total operating expenses	51,882	51,155	155,104	152,404
(Loss) gain on sale or write down of assets, net	5	(47)	(400)	(47)
Net (loss) income	(4,901)	(4,316)	(16,545)	(14,183)
Company's equity in net (loss) income	(409)	(148)	(2,139)	(1,021)
Joint Venture | Other Joint Ventures
Revenues:
Leasing revenue	169,132	176,990	514,929	533,041
Other	15,648	11,767	40,809	31,917
Total revenues	184,780	188,757	555,738	564,958
Expenses:
Shopping center and operating expenses	58,658	61,528	177,373	183,174
Leasing expenses	1,750		5,112
Interest expense	36,021	37,968	110,614	108,356
Depreciation and amortization	63,683	61,323	205,016	184,708
Total operating expenses	160,112	160,819	498,115	476,238
(Loss) gain on sale or write down of assets, net	0	12,622	(280)	14,151
Net (loss) income	24,668	40,560	57,343	102,871
Company's equity in net (loss) income	$ 14,991	18,937	$ 36,221	52,351
NML
Expenses:
Interest expense on borrowings from related party		$ 7,148		$ 19,264