Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accumulated depreciation on operating properties	$ 633,654	$ 577,139
Real estate assets and other assets held for sale, accumulated depreciation and amortization	0	61,093
Accumulated amortization on intangible liabilities	61,084	55,798
Accumulated amortization on liabilities of real estate assets held for sale	$ 0	$ 7,771
Preferred stock, par value (in usd per share)	$ 1	$ 1
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	1,716,837
Preferred stock, shares outstanding	0	1,716,837
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	151,124,621	149,347,382
Treasury stock, shares	2,584,933	2,584,933