Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	37,121,618	41,102,538
Treasury stock, shares	8,003,086	12,052,894