Schedule III - Real Estate and Accumulated Depreciation (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Real Estate and Accumulated Depreciation [Line Items]
Accumulated depreciation, beginning of year	$ 742,503	$ 672,429	$ 605,976
Depreciation of real estate	125,906	105,982	86,288
Total additions during period	125,906	105,982	86,288
Write-offs due to sale	(109,797)	(11,152)	(3,549)
Properties held for sale	0	(14,905)	0
Other	(2,097)	(9,851)	(16,286)
Total deductions during period	(111,894)	(35,908)	(19,835)
Accumulated depreciation, end of year	$ 756,515	$ 742,503	$ 672,429