Real Estate, Other Assets and Liabilities Held For Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Assets, held for sale [Abstract]
Land	$ 0								$ 16,681				$ 0		$ 16,681
Building and tenant improvements	0								322,811				0		322,811
Land held for development	0								1,089				0		1,089
Less accumulated depreciation	0								(131,274)				0		(131,274)
Net real estate assets	0								209,307				0		209,307
Accrued straight-line rents receivable, net	0								11,730				0		11,730
Deferred leasing costs, net	0								6,690				0		6,690
Prepaid expenses and other assets, net	0								13,221				0		13,221
Real estate and other assets, net, held for sale	0								240,948				0		240,948
Liabilities [Abstract]
Accounts payable, accrued expenses and other liabilities	0								(6,717)				0		(6,717)
Financing obligation	0								(7,402)				0		(7,402)
Liabilities held for sale	0								(14,119)				0		(14,119)
Discontinued Operations [Abstract]
Rental and other revenues													8,484		50,935	$ 52,597
Operating expenses:
Rental property and other expenses													3,334		20,805	19,620
Depreciation and amortization													0		14,039	15,386
General and administrative													1,388		2,366	965
Total operating expenses													4,722		37,210	35,971
Interest expense													85		621	725
Other income													420		2,635	2,700
Income from discontinued operations													4,097		15,739	18,601
Net gains on disposition of discontinued operations													414,496		0	384
Total income from discontinued operations	$ 0	[1]	$ 0		$ 0		$ 418,593		$ 2,889	$ 4,265	$ 4,670	$ 3,915	418,593	[1]	15,739	18,985
Net Cash Provided by (Used in) Discontinued Operations [Abstract]
Cash flows from operating activities													2,040		27,579	32,485
Cash flows from investing activities													$ 417,097		$ (16,445)	$ (8,279)

[1] See Note 2 for a discussion regarding the sales of the Plaza assets.