Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Accounts receivable, allowance	$ 3.3	$ 2.6
Senior Convertible Preferred Stock, par value	$ 0.01	$ 0.01
Senior Convertible Preferred Stock, shares authorized	10,000,000	10,000,000
Senior Convertible Preferred Stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	80,000,000	80,000,000
Common Stock, shares issued	23,993,214	23,688,347
Treasury stock, shares	2,686,899	2,589,803