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Pension and Other Postretirement Benefit Plans (Tables)
3 Months Ended
Mar. 31, 2023
Retirement Benefits [Abstract]  
Components of Net Periodic Benefit Expense (Income) [Table Text Block]
 PensionOther
Postretirement
Components of Net Periodic Benefit Cost (Credit)2023202220232022
Millions    
Three Months Ended March 31,
Service Cost$1.6 $2.4 $0.6 $0.8 
Non-Service Cost Components (a)
Interest Cost 10.1 6.7 1.5 1.1 
Expected Return on Plan Assets (10.9)(10.4)(2.8)(2.4)
Amortization of Prior Service Credits — — (1.8)(1.9)
Amortization of Net Loss1.4 3.2 (0.5)0.1 
Net Periodic Benefit Cost (Credit)$2.2 $1.9 $(3.0)$(2.3)
(a)These components of net periodic benefit cost (credit) are included in the line item “Other” under Other Income (Expense) on the Consolidated Statement of Income.