v3.26.1
Interim Pension and Other Postretirement Benefit Plan Information
 6 Months Ended
Mar. 31, 2026
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 and six months ended March 31, 2026 and 2025 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 income.
 Three Months Ended March 31
 Pension BenefitsOther Benefits
 2026202520262025
 (In thousands)
Components of net periodic pension cost:
Service cost$2,580 $2,837 $2,017 $2,033 
Interest cost (1)
6,925 6,663 3,635 3,365 
Expected return on assets (1)
(7,949)(7,655)(4,070)(3,831)
Amortization of prior service cost (credit) (1)
— — (2,879)(3,260)
Amortization of actuarial (gain) loss (1)
(51)256 (2,415)(2,429)
Net periodic pension cost$1,505 $2,101 $(3,712)$(4,122)
 Six Months Ended March 31
 Pension BenefitsOther Benefits
2026202520262025
 (In thousands)
Components of net periodic pension cost:
Service cost$5,160 $5,674 $4,034 $4,066 
Interest cost (1)
13,850 13,326 7,270 6,731 
Expected return on assets (1)
(15,898)(15,309)(8,140)(7,663)
Amortization of prior service cost (credit) (1)
— — (5,759)(6,520)
Amortization of actuarial (gain) loss (1)
(102)511 (4,830)(4,858)
Net periodic pension cost$3,010 $4,202 $(7,425)$(8,244)
(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating income 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, 2025.