Real Estate - Assets and Liabilities Held-for-sale (Details) - Held-for-sale - Woodcrest and Hearst Tower - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Real estate assets and other assets held for sale
Operating properties, net of accumulated depreciation of $8,123 and $44,478 in 2020 and 2019, respectively	$ 106,864	$ 340,171
Notes and accounts receivable	439	5,520
Deferred rents receivable	2,480	5,745
Intangible assets, net of accumulated amortization of $6,065 and $16,615 in 2020 and 2019, respectively	15,830	8,657
Other assets	133	489
Total real estate assets and other assets held for sale	125,746	360,582
Liabilities of real estate assets held for sale
Accounts payable and accrued expenses	7,399	12,497
Deferred income	44	2,638
Intangible liabilities, net of accumulated amortization of $1,205 and $7,771 in 2020 and 2019, respectively	3,014	5,471
Other liabilities	2,149	625
Total liabilities of real estate assets held for sale	12,606	21,231
Operating properties, net of accumulated depreciation	8,123	44,478
Intangible assets, net of accumulated amortization	6,065	16,615
Intangible liabilities, net of accumulated amortization	$ 1,205	$ 7,771