Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Real estate assets:
Accumulated depreciation on operating properties	$ 352,350	$ 324,543
Development in Process, Accumulated Depreciation	0	0
Real Estate Held for Sale, Accumulated Depreciation	7,200	0
Finite-Lived Intangible Assets, Accumulated Amortization	103,458	76,050
Allowance for doubtful accounts for notes and other receivables	1,353	1,643
Intangible Liabilities, Accumulated Amortization	$ 26,890	$ 16,897
Preferred stock, 20,000,000 shares authorized, $1 par value:
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	350,000,000	250,000,000
Treasury stock, shares	5,584,743	3,570,082