Dispositions (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Dispositions [Abstract]
Real Estate, Net	$ 29,561	$ 2,028,677
Other Assets	7,459	205,451
Assets related to discontinued operations	37,020	2,234,128
Mortgages Payable, net	0	1,278,182
Other Liabilities (primarily deferred revenue in 2014)	12,470	222,827
Liabilities related to discontinued operations	12,470	1,501,009
Income from discontinued operations:
Total revenues	27,831	395,786	$ 502,061
Total expenses	17,651	274,107	310,364
Income from discontinued operations before gain on sale of real estate	10,180	121,679	191,697
Net gains on sale of real estate	65,396	507,192	414,502
Transaction related costs (primarily UE Spin off)	(22,972)	(14,956)	0
Impairment losses	(256)	(26,518)	(37,170)
Net gain on sale of asset other than real estate	0	0	1,377
Pretax income from discontinued operations	52,348	587,397	570,406
Income tax expense	(86)	(1,721)	(2,311)
Income from Discontinued Operations	52,262	585,676	568,095
Cash flows related to discontinued Operations:
Cash flows from operating activities, discontinued operations	(33,462)	123,837	279,436
Cash flows from investing activities, discontinued operations	$ 346,865	$ (180,019)	$ (117,497)