Variable Interest Entities - Consolidated Assets and Liabilities of VIEs (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
ASSETS
Buildings and improvements	$ 10,683,541	$ 11,239,732
Development costs and construction in progress	373,818	447,976
Land	1,655,012	1,785,865
Accumulated depreciation and amortization	(2,750,351)	(2,741,695)
Net real estate	9,962,020	10,731,878
Investments in and advances to unconsolidated joint ventures	628,607	800,840
Accounts receivable, net	43,965	40,733
Cash and cash equivalents	91,381	55,306	$ 391,965
Restricted cash	30,548	26,897	$ 61,481
Intangible assets, net	294,056	410,082
Other assets, net	554,400	578,033
Total assets	13,451,387	14,088,461
LIABILITIES AND EQUITY
Mortgage debt	140,321	144,486
Intangible liabilities, net	49,976	52,579
Accounts payable and accrued liabilities	10,357	14,031
Total liabilities	8,034,664	8,493,523
VIEs
ASSETS
Buildings and improvements	1,537,928	2,436,414
Development costs and construction in progress	21,929	32,285
Land	128,889	227,162
Accumulated depreciation and amortization	(348,974)	(542,091)
Net real estate	1,339,772	2,153,770
Investments in and advances to unconsolidated joint ventures	1,897	2,231
Accounts receivable, net	7,251	10,242
Cash and cash equivalents	10,928	15,861
Restricted cash	2,951	2,619
Intangible assets, net	88,257	125,475
Other assets, net	33,336	33,749
Total assets	1,484,392	2,343,947
LIABILITIES AND EQUITY
Mortgage debt	44,789	45,016
Intangible liabilities, net	11,261	10,672
Accounts payable and accrued liabilities	55,573	269,280
Deferred revenue	15,606	14,432
Total liabilities	$ 127,229	$ 339,400