Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in usd per share)	$ 5	$ 5
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	185,744,072	185,744,072
Treasury stock, shares	46,302,744	46,743,601