Real Estate, Other Assets and Liabilities Held for Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Assets, held for sale [Abstract]
Real estate and other assets, net, held for sale	$ 54,543		$ 54,543		$ 0
Liabilities, held for sale [Abstract]
Liabilities held for sale	(1,122)		(1,122)		0
Operating expenses:
Income from discontinued operations	0	$ 0	0	$ 4,097
Net gains on disposition of discontinued operations	0	0	0	414,496
Total income from discontinued operations	0	0	0	418,593
Disposal Group, Real Estate, Other Assets and Liabilities Held For Sale [Member]
Assets, held for sale [Abstract]
Land	11,610		11,610		0
Buildings and tenant improvements	69,259		69,259		0
Less-accumulated depreciation	(30,399)		(30,399)		0
Net real estate assets	50,470		50,470		0
Accrued straight-line rents receivable, net	2,284		2,284		0
Deferred leasing costs, net	1,740		1,740		0
Prepaid expenses and other assets	49		49		0
Real estate and other assets, net, held for sale	54,543		54,543		0
Liabilities, held for sale [Abstract]
Accounts payable, accrued expenses and other liabilities	(1,122)		(1,122)		0
Liabilities held for sale	(1,122)		(1,122)		$ 0
Disposal Group, Discontinued Operations [Member]
Discontinued Operations [Abstract]
Rental and other revenues	0	0	0	8,484
Operating expenses:
Rental property and other expenses	0	0	0	3,334
General and administrative	0	0	0	1,388
Total operating expenses	0	0	0	4,722
Interest expense	0	0	0	85
Other income	0	0	0	420
Income from discontinued operations	0	0	0	4,097
Net gains on disposition of discontinued operations	0	0	0	414,496
Total income from discontinued operations	$ 0	$ 0	0	418,593
Net Cash Provided by/(Used in) Discontinued Operations [Abstract]
Cash flows from operating activities			0	2,040
Cash flows from investing activities			$ 0	$ 417,097