Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 2.5	$ 2.5
Common stock, shares authorized (in shares)	600,000,000	600,000,000
Common stock, shares issued (in shares)	219,000,000	218,900,000
Treasury stock, shares (in shares)	45,900,000	44,700,000