Variable Interest Entities - Consolidated Assets and Liabilities of VIEs (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
ASSETS
Buildings and improvements	$ 11,052,578	$ 11,692,654
Developments in process	429,459	400,619
Land	1,752,890	1,881,487
Accumulated depreciation	(2,699,174)	(2,648,930)
Net real estate	10,535,753	11,325,830
Investments in and advances to unconsolidated joint ventures	822,369	571,491
Accounts receivable, net	34,571	45,116
Cash and cash equivalents	133,887	94,730	$ 132,891	$ 346,500
Restricted cash	27,135	42,260
Intangible assets, net	400,867	479,805
Other assets, net	616,169	711,624
Total assets	13,904,081	15,759,265
LIABILITIES AND EQUITY
Mortgage debt	145,417	623,792
Intangible liabilities, net	53,427	58,145
Accounts payable and accrued expenses	8,653	3,776
Deferred revenue	140,378	149,181
Total liabilities	8,049,850	9,817,957
VIEs
ASSETS
Buildings and improvements	2,833,834	3,522,310
Developments in process	22,860	31,953
Land	227,682	327,241
Accumulated depreciation	(584,621)	(676,276)
Net real estate	2,499,755	3,205,228
Investments in and advances to unconsolidated joint ventures	2,119	3,641
Accounts receivable, net	9,964	19,996
Cash and cash equivalents	36,262	35,844
Restricted cash	2,137	22,624
Intangible assets, net	132,905	169,027
Other assets, net	56,854	69,562
Total assets	2,739,996	3,525,922
LIABILITIES AND EQUITY
Mortgage debt	45,067	520,870
Intangible liabilities, net	9,170	8,994
Accounts payable and accrued expenses	102,780	120,719
Deferred revenue	18,162	23,456
Total liabilities	$ 175,179	$ 674,039