Variable Interest Entities - Consolidated Assets and Liabilities of VIEs (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
ASSETS
Buildings and improvements	$ 10,956,474	$ 11,239,732
Development costs and construction in progress	442,007	447,976
Land	1,663,069	1,785,865
Accumulated depreciation and amortization	(2,825,850)	(2,741,695)
Net real estate	10,235,700	10,731,878
Investments in and advances to unconsolidated joint ventures	623,255	800,840
Accounts receivable, net	48,701	40,733
Cash and cash equivalents	78,864	55,306	$ 133,887
Restricted cash	29,877	26,897	$ 27,135
Intangible assets, net	305,805	410,082
Other assets, net	582,682	578,033
Total assets	13,083,958	14,088,461
LIABILITIES AND EQUITY
Mortgage debt	139,401	144,486
Intangible liabilities, net	56,871	52,579
Accounts payable and accrued liabilities	3,146	14,031
Deferred revenue	174,509	144,709
Total liabilities	7,443,583	8,493,523
VIEs
ASSETS
Buildings and improvements	2,029,066	2,436,414
Development costs and construction in progress	37,581	32,285
Land	155,807	227,162
Accumulated depreciation and amortization	(352,879)	(542,091)
Net real estate	1,869,575	2,153,770
Investments in and advances to unconsolidated joint ventures	1,641	2,231
Accounts receivable, net	5,761	10,242
Cash and cash equivalents	20,028	15,861
Restricted cash	3,362	2,619
Intangible assets, net	146,701	125,475
Other assets, net	34,884	33,749
Total assets	2,081,952	2,343,947
LIABILITIES AND EQUITY
Mortgage debt	44,694	45,016
Intangible liabilities, net	32,058	10,672
Accounts payable and accrued liabilities	71,580	269,280
Deferred revenue	17,969	14,432
Total liabilities	$ 166,301	$ 339,400