Real Estate and Accumulated Depreciation (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Real Estate
Balance at beginning of year	$ 9,468,165,000	$ 9,718,978,000	$ 11,000,496,000
Additions during the year:
Newly consolidated assets		69,410,000	19,683,000
Acquisitions	44,681,000
Capital additions	207,263,000	175,329,000	275,444,000
Deductions during the year:
Casualty and other write-offs	(192,542,000)	(15,865,000)	(43,134,000)
Sales	(610,430,000)	(479,687,000)	(1,533,511,000)
Balance at end of year	8,917,137,000	9,468,165,000	9,718,978,000
Accumulated Depreciation
Balance at beginning of year	2,934,912,000	2,723,844,000	2,815,497,000
Additions during the year
Depreciation	382,213,000	422,099,000	478,550,000
Newly consolidated assets		(12,348,000)	(2,763,000)
Deductions during the year:
Casualty and other write-offs	(173,941,000)	(4,831,000)	(5,200,000)
Sales	(270,994,000)	(193,852,000)	(562,240,000)
Balance at end of year	2,872,190,000	2,934,912,000	2,723,844,000
Real Estate and Accumulated Depreciation (Textual) [Abstract]
Write-off of fully depreciated assets	$ 165,900,000