Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value	$ 5	$ 5
Common stock, authorized shares	325,000,000	325,000,000
Common stock, issued shares	228,164,824	228,164,824
Shares in treasury	52,851,156	52,457,113