CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts receivable, allowance for credit losses, current	$ 0.0	$ 0.0
Preferred Stock, shares authorized (in shares)	100,000,000
Preferred Stock, shares outstanding (in shares)	0
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)	176,300,000	140,500,000
Common Stock, shares outstanding (in shares)	133,300,000	97,800,000
Treasury stock (in shares)	43,000,000.0	42,700,000
Preferred Stock
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
Common Stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized (in shares)	50,000,000	50,000,000.0
Common Stock, shares issued (in shares)	0	0
Common Stock, shares outstanding (in shares)	0	0
Common Stock
Common Stock, par value per share (in dollars per share)	$ 0.01
Common Stock, shares authorized (in shares)	450,000,000