Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Condensed Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 7.0	$ 6.9
Common stock stated value per share	$ 20.00	$ 20.00
Authorized	50,000,000	50,000,000
Issued to voting trustees	19,182,922	18,755,472
Issued to shareholders	3,979,373	3,905,994
In treasury, at cost	(274,887)	(57,047)
Outstanding Common Stock	22,887,408	22,604,419