Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Series A Preferred Stock [Member]	Dec. 31, 2010 Series A Preferred Stock [Member]	Dec. 31, 2011 Series B Preferred Stock [Member]	Dec. 31, 2010 Series B Preferred Stock [Member]
Accumulated depreciation on operating properties	$ 289,473	$ 274,925
Allowance for doubtful accounts for notes and other receivables	$ 5,100	$ 6,287
Preferred stock, dividend rate			7.75%	7.75%	7.50%	7.50%
Preferred stock, shares issued			2,993,090	2,993,090	3,791,000	3,791,000
Preferred stock, shares outstanding			2,993,090	2,993,090	3,791,000	3,791,000
Preferred stock, liquidation preference			$ 25	$ 25	$ 25	$ 25
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	20,000,000	20,000,000
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	107,272,078	106,961,959
Treasury stock, shares	3,570,082	3,570,082