Unaudited Condensed Consolidated Balance Sheet (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Stockholders' Equity:
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	192,428,122	191,935,647
Common stock, shares outstanding	184,011,668	186,614,747