Variable Interest Entities - Consolidated Assets and Liabilities of VIEs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
ASSETS
Buildings and improvements	$ 11,532,338	$ 11,239,732
Development costs and construction in progress	344,948	447,976
Land	1,808,210	1,785,865
Accumulated depreciation and amortization	(2,826,325)	(2,741,695)
Net real estate	10,859,171	10,731,878
Investments in and advances to unconsolidated joint ventures	863,775	800,840
Accounts receivable, net	51,468	40,733
Cash and cash equivalents	86,021	55,306	$ 764,114
Restricted cash	31,947	26,897	$ 60,806
Intangible assets, net	395,298	410,082
Other assets, net	583,261	578,033
Total assets	14,067,571	14,088,461
LIABILITIES AND EQUITY
Mortgage debt	143,524	144,486
Intangible liabilities, net	52,576	52,579
Accounts payable and accrued liabilities	8,564	14,031
Deferred revenue	167,975	144,709
Total liabilities	8,586,648	8,493,523
VIEs
ASSETS
Buildings and improvements	1,744,402	2,436,414
Development costs and construction in progress	16,226	32,285
Land	170,889	227,162
Accumulated depreciation and amortization	(345,331)	(542,091)
Net real estate	1,586,186	2,153,770
Investments in and advances to unconsolidated joint ventures	2,148	2,231
Accounts receivable, net	7,287	10,242
Cash and cash equivalents	12,077	15,861
Restricted cash	2,595	2,619
Intangible assets, net	111,149	125,475
Other assets, net	35,788	33,749
Total assets	1,757,230	2,343,947
LIABILITIES AND EQUITY
Mortgage debt	44,882	45,016
Intangible liabilities, net	12,509	10,672
Accounts payable and accrued liabilities	223,708	269,280
Deferred revenue	15,275	14,432
Total liabilities	$ 296,374	$ 339,400