Dispositions (Details 1) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Dispositions [Abstract]
Real Estate, Net	$ 27,560			$ 27,560		$ 2,028,677
Other Assets	7,582			7,582		215,804
Assets related to discontinued operations	35,142			35,142		2,244,481
Mortgages Payable	0			0		1,288,535
Other Liabilities (primarily deferred revenue in 2014)	11,520			11,520		222,827
Liabilities related to discontinued operations	11,520			11,520		$ 1,511,362
Income from discontinued operations:
Total revenues	2,589		$ 93,440	24,868	$ 297,039
Total expenses	1,279		62,715	16,672	204,619
Income from discontinued operations before gain on sale of real estate	1,310		30,725	8,196	92,420
Net gains on sale of real estate	0	$ 3,675	57,796	10,867	57,796
Transaction related costs (primarily UE Spin off)	0		(5,828)	(22,972)	(9,343)
Net gain on sale of lease position in Geary Street, CA	0		0	21,376	0
Impairment losses	0		0	(256)	(20,842)
Pretax income from discontinued operations	34,463		82,693	50,364	120,031
Income tax expense	0		(525)	(86)	(1,575)
Income from Discontinued Operations	34,463		82,168	50,278	118,456
Cash flows related to discontinued Operations:
Cash flows from operating activities, discontinued operations				(34,490)	153,815
Cash flows from investing activities, discontinued operations				348,697	(122,247)
Monmouth Mall [Member]
Income from discontinued operations:
Net gains on sale of real estate	$ 33,153		$ 0	$ 33,153	$ 0