Investments in Unconsolidated Joint Ventures - Combined Condensed Statements of Operations of unconsolidated joint ventures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Leasing revenue	$ 211,022		$ 422,030
Expenses:
Company's equity in net (loss) income	7,257	$ 15,669	19,500	$ 32,541
Joint Venture
Revenues:
Leasing revenue	217,619	220,970	437,163	446,833
Other	13,532	12,311	25,778	20,750
Total revenues	231,151	233,281	462,941	467,583
Expenses:
Shopping center and operating expenses	67,535	69,842	136,857	140,844
Leasing expenses	2,028		4,202
Interest expense	54,725	54,126	108,587	103,884
Depreciation and amortization	101,598	85,044	191,579	171,940
Total operating expenses	225,886	209,012	441,225	416,668
(Loss) gain on sale or write down of assets, net	(544)	559	(685)	1,529
Net (loss) income	4,721	24,828	21,031	52,444
Company's equity in net (loss) income	7,257	15,669	19,500	32,541
NML
Expenses:
Interest expense on borrowings from related party		7,158		12,116
PPR Portfolio | Joint Venture
Revenues:
Leasing revenue	45,346	45,362	91,366	90,782
Other	435	432	617	600
Total revenues	45,781	45,794	91,983	91,382
Expenses:
Shopping center and operating expenses	8,470	9,517	18,142	19,198
Leasing expenses	373		840
Interest expense	17,043	16,770	33,994	33,496
Depreciation and amortization	24,732	24,071	50,246	48,555
Total operating expenses	50,618	50,358	103,222	101,249
(Loss) gain on sale or write down of assets, net	(399)	0	(405)	0
Net (loss) income	(5,236)	(4,564)	(11,644)	(9,867)
Company's equity in net (loss) income	(531)	(257)	(1,730)	(873)
Other Joint Ventures | Joint Venture
Revenues:
Leasing revenue	172,273	175,608	345,797	356,051
Other	13,097	11,879	25,161	20,150
Total revenues	185,370	187,487	370,958	376,201
Expenses:
Shopping center and operating expenses	59,065	60,325	118,715	121,646
Leasing expenses	1,655		3,362
Interest expense	37,682	37,356	74,593	70,388
Depreciation and amortization	76,866	60,973	141,333	123,385
Total operating expenses	175,268	158,654	338,003	315,419
(Loss) gain on sale or write down of assets, net	(145)	559	(280)	1,529
Net (loss) income	9,957	29,392	32,675	62,311
Company's equity in net (loss) income	$ 7,788	$ 15,926	$ 21,230	$ 33,414