Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 6.9	$ 6.2
Common stock stated value per share	$ 20.00	$ 20.00
Authorized	50,000,000	50,000,000
Issued to voting trustees	18,755,472	18,665,064
Issued to shareholders	3,905,994	3,872,159
In treasury, at cost	(57,047)	(62,700)
Outstanding Common Stock	22,604,419	22,474,523
Common shares subscribed	1,052,817	997,275
Less subscripton receivable	(1,052,817)	(997,275)