Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Accounts receivable, allowances for bad debts and book returns	$ 8.2	$ 8.4
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	380,000,000	380,000,000
Common stock, shares issued	151,987,387	150,459,034
Common stock, shares outstanding	127,410,353	125,882,000
Treasury stock, shares	24,577,034	24,577,034