Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables allowance	$ 6.0	$ 6.5
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, authorized shares	5,000,000	5,000,000
Preferred stock, unissued shares	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized shares	200,000,000	200,000,000
Common stock, shares outstanding	60,759,416	61,839,734
Treasury, shares	17,713,502	16,613,193