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CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) (Parenthetical) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2023
Sep. 30, 2022
Sep. 30, 2023
Sep. 30, 2022
Statement of Comprehensive Income [Abstract]        
Postretirement adjustments $ 7.0 $ 14.4 $ (0.4) $ 35.2