CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets
Allowance for doubtful accounts	$ 8.8	$ 7.7
Stockholders' equity
Common stock, shares authorized (shares)	400,000,000.0	400,000,000.0
Common stock, shares issued (shares)	258,400,000	289,300,000
Treasury shares (shares)	8,300,000	300,000