Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, shares outstanding	5,200,000	5,200,000
Common stock, par value (per share)	$ 1.00	$ 1.00
Common stock, shares authorized	342,857,143	342,857,143
Common stock, shares issued (in shares)	142,025,720	140,592,409
Common stock, shares outstanding	122,266,106	129,547,032
Treasury stock, shares at cost	19,759,614	11,045,377