Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value (dollars per share)	$ 0.10	$ 0.10
Preferred stock, authorized (shares)	5,000,000	5,000,000
Preferred stock, issued (shares)	0	0
Preferred stock, outstanding (shares)	0	0
Common stock, par value (dollars per share)	$ 0.20	$ 0.20
Common stock, authorized (shares)	500,000,000	500,000,000
Common stock, issued (shares)	123,307,837	126,748,836
Common stock, outstanding (shares)	123,307,837	126,748,836
Treasury stock, at cost (shares)	111,810,081	108,369,082