Schedule III - REAL ESTATE AND ACCUMLATED DEPRECIATION (Details2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Real Estate
Balance at beginning of year	$ 2,589,730,000	$ 2,161,977,000	$ 2,680,647,000
Change in land	66,889,000	69,110,000	13,240,000
Additions	179,372,000	452,461,000	116,482,000
Impairments			(503,356,000)
Dispositions and write-offs and land costs of sales	(89,395,000)	(93,818,000)	(145,036,000)
Balance at end of year	2,746,596,000	2,589,730,000	2,161,977,000
Reconciliation of Accumulated Depreciation
Balance at beginning of year	91,605,000	78,931,000	81,180,000
Depreciation Expense	19,457,000	14,012,000	14,582,000
Dispositions and write-offs	1,429,000	(1,338,000)	(16,831,000)
Balance at end of year	112,491,000	91,605,000	78,931,000
Aggregate cost of land, building ad improvements for federal income tax purposes	$ 2,600,000,000
Building, improvements and carrying costs | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	10 years
Building, improvements and carrying costs | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	45 years
Equipment, tenant improvements and fixtures | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	5 years
Equipment, tenant improvements and fixtures | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	10 years
Computer hardware and software, and vehicles | Minimum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	3 years
Computer hardware and software, and vehicles | Maximum
REAL ESTATE AND ACCUMULATED DEPRECIATION
Estimated useful lives of assets	5 years