Consolidated balance sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	75,000,000	25,000,000
Common stock, shares issued	24,107,660	17,180,000
Common stock, shares outstanding	24,107,660	17,180,000