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Interim Pension and Other Postretirement Benefit Plan Information
 3 Months Ended
Dec. 31, 2020
Retirement Benefits, Description [Abstract]  
Interim Pension and Other Postretirement Benefit Plan Information Interim Pension and Other Postretirement Benefit Plan Information
The components of our net periodic pension cost for our pension and other postretirement benefit plans for the three months ended December 31, 2020 and 2019 are presented in the following tables. Most of these costs are recoverable through our tariff rates. A portion of these costs is capitalized into our rate base or deferred as a regulatory asset or liability. The remaining costs are recorded as a component of operation and maintenance expense or other non-operating expense.
 Three Months Ended December 31
 Pension BenefitsOther Benefits
 2020201920202019
 (In thousands)
Components of net periodic pension cost:
Service cost$4,612 $4,653 $4,306 $3,366 
Interest cost(1)
5,028 5,843 2,660 2,653 
Expected return on assets(1)
(6,978)(7,079)(2,614)(2,625)
Amortization of prior service cost (credit)(1)
(58)(58)43 43 
Amortization of actuarial (gain) loss(1)
3,172 (1,271)— (334)
Net periodic pension cost$5,776 $2,088 $4,395 $3,103 
(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating expense in the condensed consolidated statements of comprehensive income or are capitalized on the condensed consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020.
For the three months ended December 31, 2020 we contributed $4.1 million to our postretirement medical plans. We anticipate contributing a total of between $15 million and $25 million to our postretirement plans during fiscal 2021.