Real Estate, Other Assets and Liabilities Held For Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Assets [Abstract]
Land	$ 0		$ 0		$ 16,681
Buildings and tenant improvements	0		0		322,811
Land held for development	260		260		1,089
Less - accumulated depreciation	0		0		(131,274)
Net real estate assets	260		260		209,307
Accrued straight-line rents receivable, net	0		0		11,730
Deferred leasing costs, net	0		0		6,690
Prepaid expenses and other assets, net	0		0		13,221
Real estate and other assets, net, held for sale	260		260		240,948
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	0		0		(6,717)
Financing obligation	0		0		(7,402)
Liabilities held for sale	0		0		$ (14,119)
Discontinued Operations [Abstract]
Rental and other revenues	0	$ 12,970	8,484	$ 37,637
Operating expenses:
Rental property and other expenses	0	5,328	3,334	15,235
Depreciation and amortization	0	3,689	0	10,442
General and administrative	0	192	1,388	613
Total operating expenses	0	9,209	4,722	26,290
Interest expense	0	155	85	491
Other income	0	659	420	1,994
Income from discontinued operations	0	4,265	4,097	12,850
Net gains on disposition of discontinued operations	0	0	414,496	0
Total income from discontinued operations	$ 0	$ 4,265	418,593	12,850
Net Cash Provided by/(Used in) Discontinued Operations [Abstract]
Cash flows from operating activities			2,040	21,991
Cash flows from investing activities			$ 417,097	$ (12,642)