Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Accumulated depreciation on operating properties	$ 971,023	$ 874,988
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	154,024,945	151,272,969
Common stock, shares outstanding (in shares)	154,024,945	151,272,969
Treasury stock, shares (in shares)	2,584,933	2,584,933