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Components of Net Periodic Benefit Cost
9 Months Ended
Sep. 30, 2021
Retirement Benefits [Abstract]  
Components of Net Periodic Benefit Cost
Note 2 – Components of Net Periodic Benefit Cost
Southwest has a noncontributory qualified retirement plan with defined benefits covering substantially all employees and a separate unfunded supplemental retirement plan (“SERP”) which is limited to officers. Southwest also provides postretirement benefits other than pensions (“PBOP”) to its qualified retirees for health care, dental, and life insurance.
The service cost component of net periodic benefit costs included in the table below is a component of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of service cost to the same accounts to which productive labor is charged. As a result, service costs become components of various accounts, primarily operations and maintenance expense, net utility plant, and deferred charges and other assets for both the Company and Southwest. The other components of net periodic benefit cost are reflected in Other income (deductions) on the Condensed Consolidated Statements of Income of each entity.
 Qualified Retirement Plan
 September 30,
 Three MonthsNine MonthsTwelve Months
 202120202021202020212020
(Thousands of dollars)      
Service cost$10,289 $8,576 $30,869 $25,725 $39,443 $32,191 
Interest cost10,108 11,388 30,324 34,165 41,714 46,416 
Expected return on plan assets(18,088)(16,324)(54,264)(48,972)(70,588)(64,033)
Amortization of net actuarial loss10,489 9,006 31,467 27,019 40,473 32,608 
Net periodic benefit cost$12,798 $12,646 $38,396 $37,937 $51,042 $47,182 
 SERP
 September 30,
 Three MonthsNine MonthsTwelve Months
 202120202021202020212020
(Thousands of dollars)      
Service cost$131 $97 $394 $292 $491 $359 
Interest cost358 401 1,074 1,204 1,474 1,644 
Amortization of net actuarial loss661 451 1,981 1,353 2,433 1,608 
Net periodic benefit cost$1,150 $949 $3,449 $2,849 $4,398 $3,611 
 PBOP
 September 30,
 Three MonthsNine MonthsTwelve Months
 202120202021202020212020
(Thousands of dollars)      
Service cost$423 $395 $1,269 $1,186 $1,664 $1,505 
Interest cost549 646 1,645 1,936 2,291 2,697 
Expected return on plan assets(810)(852)(2,430)(2,556)(3,282)(3,345)
Amortization of prior service costs239 289 719 867 1,007 1,185 
Net periodic benefit cost$401 $478 $1,203 $1,433 $1,680 $2,042 
For new employees hired on or after January 1, 2022, the defined benefit retirement plan will be replaced with enhanced contributions to the 401(k) plan. The change is not applicable to existing employees, nor to employees hired during the remainder of 2021. Current employees will continue to be eligible to receive employer 401(k) matching contributions on one-half of amounts deferred by them, up to a maximum matching contribution of 3.5% of their eligible annual compensation. Employees hired after 2021 will be eligible for enhanced employer 401(k) contributions of 3% plus a matching contribution (dollar-for-dollar) up to 7% of eligible compensation.