CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Current assets
Allowance for credit losses	$ 0.0	$ 0.0
Stockholders' equity
Treasury stock, shares (in shares)	43,000,000.0	42,700,000
Preferred Stock
Stockholders' equity
Preferred stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	100,000,000.0	100,000,000.0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Series Common Stock
Stockholders' equity
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	50,000,000.0	50,000,000.0
Common stock, shares issued (in shares)	0	0
Common stock, shares outstanding (in shares)	0	0
Common Stock
Stockholders' equity
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	450,000,000.0	450,000,000.0
Common stock, shares issued (in shares)	165,300,000	140,500,000
Common stock, shares outstanding (in shares)	122,300,000	97,800,000