Discontinued Operations (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Disposal Group Including Discontinued Operation Unclassified Balance Sheet Disclosures Abstract
Assets related to discontinued operations	$ 260,798		$ 565,962
Liabilities related to discontinued operations	103,609		420,508
Discontinued Operation, Income (Loss) from Discontinued Operations Disclosure [Abstract]
Total revenues	23,686	59,934
Total expenses	17,440	44,379
Income from discontinued operations before gain on sale of real estate	6,246	15,555
Impairment loss	(1,514)	0
Income from discontinued operations	207,061	71,372
Retail Properties Segment [Member]
Disposal Group Including Discontinued Operation Unclassified Balance Sheet Disclosures Abstract
Assets related to discontinued operations	229,081		532,463
Liabilities related to discontinued operations	103,609		420,508
Discontinued Operation, Income (Loss) from Discontinued Operations Disclosure [Abstract]
Income from discontinued operations	206,642	10,220
Other Segment [Member]
Disposal Group Including Discontinued Operation Unclassified Balance Sheet Disclosures Abstract
Assets related to discontinued operations	31,717		33,499
Liabilities related to discontinued operations	0		0
Discontinued Operation, Income (Loss) from Discontinued Operations Disclosure [Abstract]
Income from discontinued operations	$ 419	$ 60,174