Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance	$ 30.7	$ 30.2	$ 10.1	$ 11.2
Par value (in dollars per share)	$ 1	$ 1
Shares authorized (in shares)	100,000,000.0	100,000,000.0
Shares issued (in shares)	49,500,000	50,100,000
Shares outstanding (in shares)	49,500,000	50,100,000