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Pension and Other Postretirement Benefit Plans
 3 Months Ended
Mar. 31, 2021
Retirement Benefits [Abstract]  
Pension and Other Postretirement Benefit Plans [Text Block] PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS
 PensionOther
Postretirement
Components of Net Periodic Benefit Cost (Credit)2021202020212020
Millions    
Three Months Ended March 31,
Service Cost$2.7 $2.6 $0.9 $0.8 
Non-Service Cost Components (a)
Interest Cost 6.1 7.0 1.1 1.3 
Expected Return on Plan Assets (10.8)(10.7)(2.4)(2.5)
Amortization of Prior Service Credits — — (1.9)(2.0)
Amortization of Net Loss4.7 3.2 0.7 0.3 
Net Periodic Benefit Cost (Credit)$2.7 $2.1 $(1.6)$(2.1)
(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.
NOTE 9. PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS (Continued)

Employer Contributions. For the three months ended March 31, 2021, we contributed $10.3 million in cash to the defined benefit pension plans ($10.7 million for the three months ended March 31, 2020); we do not expect to make additional contributions to our defined benefit pension plans in 2021. For the three months ended March 31, 2021 and 2020, we made no contributions to our other postretirement benefit plans; we do not expect to make any contributions to our other postretirement benefit plans in 2021.