Schedule III - Real Estate and Accumulated Depreciation Reconciliation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of the year	$ 2,514,115
Acquistion and development of rental properties during the year	115,284
Dispostion of rental properties during the year	(226,918)
Impairment of rental properties during the year	(35,956)
Balance at close of year	2,366,525
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of the year	297,068
Depreciation during the year	45,604
Disposition of rental properties during the year	(7,237)
Balance at close of year	$ 335,435