Acquisitions, Dispositions, and Mortgage Funding (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Balance Sheet data (as of the period ended):
Land	$ 164,673	$ 161,875
Buildings, improvements and lease intangibles	2,637,030	2,625,538
Personal property	9,168	8,739
Real estate properties, Total	2,827,925	2,821,323
Less accumulated depreciation	(613,882)	(580,617)
Total real estate properties, net	2,214,043	2,240,706
Other assets, net (including receivables)	151,194	126,962
Assets held for sale and discontinued operations, net	18,688	3,337
Accounts payable and accrued liabilities	58,833	65,678
Other liabilities	58,722	60,175
Liabilities of discontinued operations	280	131
Discontinued Operations [Member]
Balance Sheet data (as of the period ended):
Land	0	3,835
Buildings, improvements and lease intangibles	29,425	5,566
Personal property	0	207
Real estate properties, Total	29,425	9,608
Less accumulated depreciation	(10,780)	(6,303)
Total real estate properties, net	18,645	3,305
Other assets, net (including receivables)	43	32
Assets of discontinued operations, net	43	32
Assets held for sale and discontinued operations, net	18,688	3,337
Accounts payable and accrued liabilities	23	99
Other liabilities	257	32
Liabilities of discontinued operations	$ 280	$ 131