Real Estate, Other Assets and Liabilities Held For Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Assets [Abstract]
Land	$ 0		$ 16,681
Buildings and tenant improvements	0		322,811
Land held for development	0		1,089
Less - accumulated depreciation	0		(131,274)
Net real estate assets	0		209,307
Accrued straight-line rents receivable, net	0		11,730
Deferred leasing costs, net	0		6,690
Prepaid expenses and other assets, net	0		13,221
Real estate and other assets, net, held for sale	0		240,948
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	0		(6,717)
Financing obligation	0		(7,402)
Liabilities held for sale	0		$ (14,119)
Discontinued Operations [Abstract]
Rental and other revenues	8,484	$ 12,074
Operating expenses:
Rental property and other expenses	3,334	4,999
Depreciation and amortization	0	3,441
General and administrative	1,388	194
Total operating expenses	4,722	8,634
Interest expense	85	181
Other income	420	656
Income from discontinued operations	4,097	3,915
Net gains on disposition of discontinued operations	414,496	0
Total income from discontinued operations	418,593	3,915
Net Cash Provided by/(Used in) Discontinued Operations [Abstract]
Cash flows from operating activities	2,040	6,773
Cash flows from investing activities	$ 417,097	$ (2,268)