Schedule III - Real Estate and Accumulated Depreciation and Amortization Summary (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Real Estate and Accumulated Depreciation [Line Items]
Total cost basis for federal income tax purposes	$ 4,200,000,000
Reconciliation of real estate owned:
Balance at the beginning of year	3,172,246,000	3,363,586,000	3,552,806,000
Additions during year	540,847,000	143,382,000	46,994,000
Properties sold during year	(138,041,000)	(230,397,000)	(221,875,000)
Reclassified held for sale properties	0	0	(9,381,000)
Properties impaired during the year	(10,553,000)	(103,727,000)	(3,327,000)
Translation adjustment on foreign currency	0	0	(1,432,000)
Other reclassifications	(33,000)	(598,000)	(199,000)
Balance at end of year	3,564,466,000	3,172,246,000	3,363,586,000
Reconciliation of accumulated depreciation and amortization:
Balance at the beginning of year	638,368,000	601,239,000	537,406,000
Depreciation and amortization expense	119,067,000	114,247,000	115,553,000
Accumulated depreciation and amortization of properties sold, impaired and held for sale during year	(19,367,000)	(76,939,000)	(51,478,000)
Translation adjustment on foreign currency	0	0	(242,000)
Other reclassifications	0	(179,000)	0
Balance at end of year	$ 738,068,000	$ 638,368,000	$ 601,239,000