Unconsolidated Affiliates and Noncontrolling Interests - Unconsolidated Affiliates (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
ASSETS:
Investment in real estate assets		$ 5,510,348		$ 5,510,348				$ 5,830,785
Accumulated depreciation		(2,251,613)		(2,251,613)				(2,241,421)
Net investment in real estate assets		3,280,039		3,280,039				3,617,691
Developments in progress		15,065		15,065				28,327
Total assets		4,228,147		4,228,147				4,443,740
LIABILITIES:
Mortgage and other indebtedness, net		1,019,084		1,019,084				1,184,831
Shareholders' equity:
The Company		455,119		455,119				531,843
Noncontrolling interests		60		60				2,454
Total equity		455,179	$ 612,218	455,179	$ 612,218	$ 497,084	$ 506,618	534,297	$ 653,453	$ 725,091	$ 861,865
Total liabilities, redeemable noncontrolling interests and equity		4,228,147		4,228,147				4,443,740
Total revenues	[1]	150,375	129,897	420,120	421,682
Net loss		(42,881)	(44,424)	(80,722)	(256,511)
Equity in losses of unconsolidated affiliates		(2,224)	(7,389)	(9,575)	(12,450)
BI Development II, LLC
ASSETS:
Investment in real estate assets		2,463,912		2,463,912				2,346,124
Accumulated depreciation		(925,138)		(925,138)				(862,435)
Net investment in real estate assets		1,538,774		1,538,774				1,483,689
Developments in progress		10,375		10,375				28,138
Net investment in real estate assets		1,549,149		1,549,149				1,511,827
Other assets		193,924		193,924				174,966
Total assets		1,743,073		1,743,073				1,686,793
LIABILITIES:
Mortgage and other indebtedness, net		1,575,873		1,575,873				1,439,454
Other liabilities		86,467		86,467				45,280
Total liabilities		1,662,340		1,662,340				1,484,734
Shareholders' equity:
The Company		103,214		103,214				132,350
Noncontrolling interests		(22,481)		(22,481)				69,709
Total equity		80,733		80,733				202,059
Total liabilities, redeemable noncontrolling interests and equity		1,743,073		1,743,073				$ 1,686,793
Total revenues		65,482	46,953	181,985	154,128
Net loss		(3,206)	(10,671)	(16,225)	(12,139)
Equity in losses of unconsolidated affiliates		$ (2,224)	$ (7,389)	$ (9,575)	$ (12,450)

[1] Management, development and leasing fees are included in the All Other category. See Note 4 for information on the Company's revenues disaggregated by revenue source for each of the above segments.