Segments (Summary of Segment Operating Results) (Details) ft² in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) ft² segment location	Mar. 31, 2020 USD ($)
Segments reporting
Number of reportable segments | segment	4
Total revenues	$ 190,580,000	$ 175,175,000
Depreciation and amortization	(49,308,000)	(61,637,000)
Other income (loss), net	(10,308,000)	(3,684,000)
Equity in earnings (losses) from real estate and other affiliates	15,796,000	11,349,000
Gain (loss) on extinguishment of debt	(35,915,000)	0
Gain (loss) on sale or disposal of real estate and other assets, net	0	38,124,000
Provision for impairment	0	(48,738,000)
Income (loss) before taxes	(89,364,000)	(159,182,000)
Net income (loss)	(68,159,000)	(125,082,000)
Net (income) loss attributable to noncontrolling interests	1,565,000	(52,000)
Net income (loss) attributable to common stockholders	(66,594,000)	(125,134,000)
Operating segments
Segments reporting
Total revenues	190,479,000	175,157,000
Total operating expenses	(142,630,000)	(194,572,000)
Segment operating income (loss)	47,849,000	(19,415,000)
Depreciation and amortization	(48,156,000)	(59,816,000)
Interest income (expense), net	(7,040,000)	(20,761,000)
Other income (loss), net	(10,434,000)	(3,802,000)
Equity in earnings (losses) from real estate and other affiliates	15,796,000	11,349,000
Gain (loss) on extinguishment of debt	(836,000)
Gain (loss) on sale or disposal of real estate and other assets, net		38,124,000
Provision for impairment		(48,738,000)
Income (loss) before taxes	(2,821,000)	(103,059,000)
Corporate
Segments reporting
Corporate income, expenses and other items	(65,338,000)	(22,023,000)
Operating Assets Segment
Segments reporting
Total revenues	96,439,000	114,257,000
Operating Assets Segment | Operating segments
Segments reporting
Total revenues	96,439,000	114,257,000
Total operating expenses	(47,234,000)	(52,240,000)
Segment operating income (loss)	49,205,000	62,017,000
Depreciation and amortization	(39,651,000)	(37,089,000)
Interest income (expense), net	(19,000,000)	(26,193,000)
Other income (loss), net	(10,098,000)	(59,000)
Equity in earnings (losses) from real estate and other affiliates	(11,404,000)	4,394,000
Gain (loss) on extinguishment of debt	(836,000)
Gain (loss) on sale or disposal of real estate and other assets, net		38,124,000
Provision for impairment		(48,738,000)
Income (loss) before taxes	(31,784,000)	(7,544,000)
Operating Assets Segment | Operating segments | Hospitality Revenue
Segments reporting
Total revenues	7,700,000	17,200,000
Total operating expenses	(7,900,000)	(12,900,000)
MPC Segment
Segments reporting
Total revenues	48,287,000	50,446,000
MPC Segment | Operating segments
Segments reporting
Total revenues	48,287,000	50,446,000
Total operating expenses	(23,267,000)	(23,722,000)
Segment operating income (loss)	25,020,000	26,724,000
Depreciation and amortization	(72,000)	(91,000)
Interest income (expense), net	10,757,000	8,554,000
Other income (loss), net	0	0
Equity in earnings (losses) from real estate and other affiliates	27,650,000	8,934,000
Gain (loss) on extinguishment of debt	0
Gain (loss) on sale or disposal of real estate and other assets, net		0
Provision for impairment		0
Income (loss) before taxes	$ 63,355,000	44,121,000
Seaport Segment
Segments reporting
Area of real estate property (in sqft) | ft²	453
Number of primary locations | location	3
Operating locations | location	2
Total revenues	$ 7,453,000	9,694,000
Seaport Segment | Operating segments
Segments reporting
Total revenues	7,453,000	9,694,000
Total operating expenses	(12,506,000)	(14,311,000)
Segment operating income (loss)	(5,053,000)	(4,617,000)
Depreciation and amortization	(6,835,000)	(20,875,000)
Interest income (expense), net	102,000	(5,053,000)
Other income (loss), net	(336,000)	(3,368,000)
Equity in earnings (losses) from real estate and other affiliates	(352,000)	(2,043,000)
Gain (loss) on extinguishment of debt	0
Gain (loss) on sale or disposal of real estate and other assets, net		0
Provision for impairment		0
Income (loss) before taxes	$ (12,474,000)	(35,956,000)
Seaport Segment | Tin Building
Segments reporting
Area of real estate property (in sqft) | ft²	53
Strategic Developments Segment
Segments reporting
Total revenues	$ 38,300,000	760,000
Strategic Developments Segment | Operating segments
Segments reporting
Total revenues	38,300,000	760,000
Total operating expenses	(59,623,000)	(104,299,000)
Segment operating income (loss)	(21,323,000)	(103,539,000)
Depreciation and amortization	(1,598,000)	(1,761,000)
Interest income (expense), net	1,101,000	1,931,000
Other income (loss), net	0	(375,000)
Equity in earnings (losses) from real estate and other affiliates	(98,000)	64,000
Gain (loss) on extinguishment of debt	0
Gain (loss) on sale or disposal of real estate and other assets, net		0
Provision for impairment		0
Income (loss) before taxes	$ (21,918,000)	$ (103,680,000)