SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Real Estate Properties
Balance at the beginning of the year	$ 6,357,258	$ 6,323,681	$ 6,242,257
Additions	1,074,010	876,363	627,734
Loss on asset impairment		(139,673)	(39,263)
Transfer of properties to GOV			(490,656)
Property reclassified from discontinued operations			3,163
Disposals	(229,264)	(564,695)	(19,554)
Properties reclassified to discontinued operations	(42,228)	(138,418)
Balance at the end of the year	7,244,232	6,357,258	6,323,681
Accumulated Depreciation
Balance at the beginning of the year	850,261	884,421	862,958
Additions	166,371	180,631	155,341
Loss on asset impairment		(10,458)	(9,603)
Transfer of properties to GOV			(105,513)
Property reclassified from discontinued operations			792
Disposals	(85,545)	(163,014)	(19,554)
Properties reclassified to discontinued operations	(3,083)	(41,319)
Balance at the end of the year	934,170	850,261	884,421
REAL ESTATE AND ACCUMULATED DEPRECIATION
Aggregate cost of properties for federal income tax purposes	7,764,981
Real estate property additions due to changes in foreign currency exchange	(333)	8,387
Accumulated depreciation additions due to changes in foreign currency exchange	(73)	12
Impairment charges for real estate properties, continuing operations	$ 10,355
Buildings and improvements | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives (in years)	40
Personal property | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives (in years)	12