Real Estate Transactions (Assets and Liabilities Held-for-sale) (Details) - Held-for-sale - Woodcrest and Hearst Tower $ in Thousands	Dec. 31, 2019 USD ($)
Real estate assets and other assets held for sale
Operating properties, net of accumulated depreciation of $44,478	$ 340,171
Notes and accounts receivable	5,520
Deferred rents receivable	5,745
Intangible assets, net of accumulated amortization of $16,615	8,657
Other assets	489
Total assets of discontinued operation	360,582
Liabilities of real estate assets held for sale
Accounts payable and accrued expenses	12,497
Deferred income	2,638
Intangible liabilities, net of accumulated amortization of $7,771	5,471
Other liabilities	625
Total liabilities of discontinued operation	21,231
Operating properties, net of accumulated depreciation	44,478
Intangible assets, net of accumulated amortization	16,615
Intangible liabilities, net of accumulated amortization	$ 7,771