Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 124.1	$ 128.1
Other Assets:
Accumulated amortization on intangible assets	$ 427.0	$ 425.4
SHAREHOLDERS' EQUITY:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	25,000,000	25,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	125,000,000	125,000,000
Common stock, issued (in shares)	117,725,183	117,555,991
Treasury stock at cost (in shares)	63,086,793	61,990,021