Variable Interest Entities - Balance Sheet disclosures (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Buildings and improvements	$ 10,877,248	$ 11,239,732
Developments in process	537,643	447,976
Land	1,637,506	1,785,865
Accumulated depreciation	(2,842,947)	(2,741,695)
Net real estate	10,209,450	10,731,878
Investments in and advances to unconsolidated joint ventures	540,088	800,840
Accounts receivable, net	48,171	40,733
Cash and cash equivalents	110,790	55,306
Restricted cash	29,056	26,897
Intangible assets, net	305,079	410,082
Other assets, net	591,017	578,033
Total assets	12,718,553	14,088,461	$ 15,759,265
Mortgage debt	138,470	144,486
Intangible liabilities, net	54,663	52,579
Accounts payable and accrued expenses	1,125	14,031
Deferred revenue	190,683	144,709
Total liabilities	6,205,962	8,493,523
Variable Interest Entity
Variable Interest Entity [Line Items]
Buildings and improvements	1,949,582	2,436,414
Developments in process	39,584	32,285
Land	151,746	227,162
Accumulated depreciation	(398,143)	(542,091)
Net real estate	1,742,769	2,153,770
Investments in and advances to unconsolidated joint ventures	1,550	2,231
Accounts receivable, net	7,904	10,242
Cash and cash equivalents	23,772	15,861
Restricted cash	3,399	2,619
Intangible assets, net	111,333	125,475
Other assets, net	43,149	33,749
Total assets	1,933,876	2,343,947
Mortgage debt	44,598	45,016
Intangible liabilities, net	19,128	10,672
Accounts payable and accrued expenses	66,736	269,280
Deferred revenue	24,215	14,432
Total liabilities	$ 154,677	$ 339,400