Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accumulated depreciation on operating properties	$ 561,489	$ 421,495
Accumulated amortization on intangible liabilities	$ 56,414	$ 42,473
Preferred stock, par value (in usd per share)	$ 1	$ 1
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	1,716,837	1,716,837
Preferred stock, shares outstanding	1,716,837	1,716,837
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized	300,000,000	175,000,000
Common stock, shares issued	149,347,204	107,681,130
Treasury stock, shares	2,584,933	2,584,933