Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Balance Sheet data (as of the period ended):
Land	$ 178,931	$ 161,875
Buildings, improvements and lease intangibles	2,861,935	2,625,538
Personal property	9,267	8,739
Total real estate properties	3,067,187	2,821,323
Less accumulated depreciation	(632,109)	(580,617)
Total real estate properties, net	2,435,078	2,240,706
Other assets, net (including receivables)	153,514	126,962
Assets held for sale and discontinued operations, net	6,852	3,337
Accounts payable and accrued liabilities	73,741	65,678
Other liabilities	61,064	60,175
Liabilities of discontinued operations	1,112	131
Discontinued Operations [Member]
Balance Sheet data (as of the period ended):
Land	1,578	3,835
Buildings, improvements and lease intangibles	15,400	5,566
Personal property	0	207
Total real estate properties	16,978	9,608
Less accumulated depreciation	(10,211)	(6,303)
Total real estate properties, net	6,767	3,305
Other assets, net (including receivables)	85	32
Assets of discontinued operations, net	85	32
Assets held for sale and discontinued operations, net	6,852	3,337
Accounts payable and accrued liabilities	1,091	99
Other liabilities	21	32
Liabilities of discontinued operations	$ 1,112	$ 131