Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common stock, par value	$ 1.00	$ 1.00
Common stock, shares authorized	48,000,000	48,000,000
Common stock, shares issued	21,456,880	21,456,880	21,456,880
Treasury stock, shares	8,995,310	8,713,566	8,291,947