Real Estate and Other Assets Held For Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets, held for sale [Abstract]
Land	$ 0	$ 870
Building and tenant improvements	0	21,318
Land held for development	0	355
Less accumulated depreciation	0	(9,304)
Net real estate assets	0	13,239
Accrued straight-line rents receivable, net	0	591
Deferred leasing costs, net	0	253
Prepaid expenses and other assets, net	0	35
Real estate and other assets, net, held for sale	0	14,118
Discontinued Operations [Abstract]
Rental and other revenues	0	0	$ 8,484
Operating expenses:
Rental property and other expenses	0	0	3,334
General and administrative	0	0	1,388
Total operating expenses	0	0	4,722
Interest expense	0	0	85
Other income	0	0	420
Income from discontinued operations	0	0	4,097
Net gains on disposition of discontinued operations	0	0	414,496
Total income from discontinued operations	0	0	418,593
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Cash flows from operating activities	0	0	2,040
Cash flows from investing activities	$ 0	$ 0	$ 646,738