CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Accounts receivable, (net of allowance for credit losses of $2.5 and $1.7, respectively)	$ 2.5	$ 1.7
Shareholders’ equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	39,011,096	38,955,848
Common stock, shares outstanding (in shares)	37,854,409	37,552,055
Treasury stock at cost (in shares)	1,156,687	1,403,793