Investments in Unconsolidated Joint Ventures - Combined Condensed Statements of Operations of unconsolidated joint ventures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Leasing revenue	$ 211,008	$ 218,112
Expenses:
Company's equity in net (loss) income	12,243	16,872
Joint Venture
Revenues:
Leasing revenue	219,544	225,863
Other	12,246	8,439
Total revenues	231,790	234,302
Expenses:
Shopping center and operating expenses	69,322	71,002
Leasing expenses	2,174
Interest expense	53,862	49,758
Depreciation and amortization	89,981	86,896
Total operating expenses	215,339	207,656
(Loss) gain on sale or write down of assets, net	(141)	970
Net (loss) income	16,310	27,616
Company's equity in net (loss) income	12,243	16,872
NML
Expenses:
Interest expense on borrowings from related party		4,958
PPR Portfolio | Joint Venture
Revenues:
Leasing revenue	46,020	45,420
Other	182	168
Total revenues	46,202	45,588
Expenses:
Shopping center and operating expenses	9,672	9,681
Leasing expenses	467
Interest expense	16,951	16,726
Depreciation and amortization	25,514	24,484
Total operating expenses	52,604	50,891
(Loss) gain on sale or write down of assets, net	(6)	0
Net (loss) income	(6,408)	(5,303)
Company's equity in net (loss) income	(1,199)	(616)
Other Joint Ventures | Joint Venture
Revenues:
Leasing revenue	173,524	180,443
Other	12,064	8,271
Total revenues	185,588	188,714
Expenses:
Shopping center and operating expenses	59,650	61,321
Leasing expenses	1,707
Interest expense	36,911	33,032
Depreciation and amortization	64,467	62,412
Total operating expenses	162,735	156,765
(Loss) gain on sale or write down of assets, net	(135)	970
Net (loss) income	22,718	32,919
Company's equity in net (loss) income	$ 13,442	$ 17,488