Note 5 - Retirement Plans (Tables)
|
12 Months Ended |
Dec. 31, 2023 |
| Notes Tables |
|
| Schedule of Net Funded Status [Table Text Block] |
| Funded Status | | | | | | | | |
| Millions | | 2023 | | | 2022 | |
| Projected Benefit Obligation | | | | | | | | |
| Projected benefit obligation at beginning of year | | $ | 3,725 | | | $ | 5,296 | |
| Service cost | | | 52 | | | | 93 | |
| Interest cost | | | 187 | | | | 123 | |
| Actuarial loss/(gain) | | | 146 | | | | (1,557 | ) |
| Gross benefits paid | | | (230 | ) | | | (230 | ) |
| Projected benefit obligation at end of year | | $ | 3,880 | | | $ | 3,725 | |
| Plan Assets | | | | | | | | |
| Fair value of plan assets at beginning of year | | $ | 4,363 | | | $ | 5,554 | |
| Actual return/(loss) on plan assets | | | 235 | | | | (992 | ) |
| Non-qualified plan benefit contributions | | | 32 | | | | 31 | |
| Gross benefits paid | | | (230 | ) | | | (230 | ) |
| Fair value of plan assets at end of year | | $ | 4,400 | | | $ | 4,363 | |
| Funded status at end of year | | $ | 520 | | | $ | 638 | |
|
| Schedule of Amounts Recognized in Balance Sheet [Table Text Block] |
| Millions | | 2023 | | | 2022 | |
| Noncurrent assets | | $ | 924 | | | $ | 1,033 | |
| Current liabilities | | | (31 | ) | | | (31 | ) |
| Noncurrent liabilities | | | (373 | ) | | | (364 | ) |
| Net amounts recognized at end of year | | $ | 520 | | | $ | 638 | |
|
| Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] |
| Millions | | 2023 | | | 2022 | | | 2021 | |
| Net actuarial (loss)/gain | | $ | (159 | ) | | $ | 272 | | | $ | 813 | |
| Amortization of: | | | | | | | | | | | | |
| Actuarial loss | | | 9 | | | | 86 | | | | 141 | |
| Total | | $ | (150 | ) | | $ | 358 | | | $ | 954 | |
|
| Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Table Text Block] |
| Underfunded Accumulated Benefit Obligation | | | | | | | | |
| Millions | | 2023 | | | 2022 | |
| Projected benefit obligation | | $ | 404 | | | $ | 394 | |
| Accumulated benefit obligation | | $ | 399 | | | $ | 382 | |
| Fair value of plan assets | | | - | | | | - | |
| Underfunded accumulated benefit obligation | | $ | (399 | ) | | $ | (382 | ) |
|
| Defined Benefit Plan, Assumptions [Table Text Block] |
| Percentages | | 2023 | | | 2022 | |
| Discount rate | | | 5.00 | % | | | 5.21 | % |
| Compensation increase | | | 4.00 | % | | | 4.10 | % |
| Percentages | | 2023 | | | 2022 | | | 2021 | |
| Discount rate for benefit obligations | | | 5.21 | % | | | 2.80 | % | | | 2.42 | % |
| Discount rate for interest on benefit obligations | | | 5.14 | % | | | 2.40 | % | | | 1.90 | % |
| Discount rate for service cost | | | 5.19 | % | | | 2.91 | % | | | 2.61 | % |
| Discount rate for interest on service cost | | | 5.21 | % | | | 2.86 | % | | | 2.53 | % |
| Expected return on plan assets | | | 5.25 | % | | | 6.25 | % | | | 6.25 | % |
| Compensation increase | | | 4.10 | % | | | 4.10 | % | | | 4.40 | % |
|
| Schedule of Net Benefit Costs [Table Text Block] |
| Millions | | 2023 | | | 2022 | | | 2021 | |
| Net Periodic Pension Cost: | | | | | | | | | | | | |
| Service cost | | $ | 52 | | | $ | 93 | | | $ | 110 | |
| Interest cost | | | 187 | | | | 123 | | | | 104 | |
| Expected return on plan assets | | | (248 | ) | | | (293 | ) | | | (270 | ) |
| Amortization of: | | | | | | | | | | | | |
| Actuarial loss | | | 9 | | | | 86 | | | | 141 | |
| Net periodic pension cost | | $ | - | | | $ | 9 | | | $ | 85 | |
|
| Cash Contributions for Qualified Pension Plan, Benefit Payments for Non Qualified OPEB Plans [Table Text Block] |
| Millions | | Qualified | | | Non-qualified | |
| 2023 | | $ | - | | | $ | 32 | |
| 2022 | | $ | - | | | $ | 31 | |
|
| Schedule of Expected Benefit Payments [Table Text Block] |
| Millions | | | | |
| 2024 | | $ | 230 | |
| 2025 | | | 229 | |
| 2026 | | | 229 | |
| 2027 | | | 230 | |
| 2028 | | | 231 | |
| Years 2029 - 2033 | | $ | 1,188 | |
|
| Schedule of Allocation of Plan Assets [Table Text Block] |
| | | | Percentage of Plan Assets | |
| | Target | December 31, | |
| | Allocation 2024 | 2023 | | | 2022 | |
| Equity securities | | | 20% to 30% | | | | 24 | % | | | 48 | % |
| Debt securities | | | 70% to 80% | | | | 75 | | | | 51 | |
| Real estate | | | 0% to 2% | | | | 1 | | | | 1 | |
| Total | | | | 100 | % | | | 100 | % |
|
| Defined Benefit Plan, Plan Assets, Category [Table Text Block] |
| | Quoted Prices | Significant | | | |
| | in Active | Other | Significant | | |
| | Markets for | Observable | Unobservable | | |
| | Identical Inputs | Inputs | Inputs | | |
| Millions | (Level 1) | (Level 2) | (Level 3) | Total | |
| Plan assets at fair value: | | | | | | | | | | | | | | | | |
| Temporary cash investments | | $ | - | | | $ | - | | | $ | - | | | $ | - | |
| Registered investment companies [a] | | | - | | | | - | | | | - | | | | - | |
| Federal government securities | | | - | | | | 1,508 | | | | - | | | | 1,508 | |
| Bonds and debentures | | | - | | | | 1,696 | | | | - | | | | 1,696 | |
| Corporate stock | | | 176 | | | | 5 | | | | - | | | | 181 | |
| Total plan assets at fair value | | $ | 176 | | | $ | 3,209 | | | $ | - | | | $ | 3,385 | |
| Plan assets at NAV: | | | | | | | | | | | | | | | | |
| Registered investment companies [b] | | | | | | | | | | | | | | | - | |
| Venture capital and buyout partnerships | | | | | | | | | | | | | | | 554 | |
| Real estate funds | | | | | | | | | | | | | | | 30 | |
| Collective trust and other funds | | | | | | | | | | | | | | | 382 | |
| Total plan assets at NAV | | | | | | | | | | | | | | $ | 966 | |
| Other assets/(liabilities) [c] | | | | | | | | | | | | | | | 49 | |
| Total plan assets | | | | | | | | | | | | | | $ | 4,400 | |
| | Quoted Prices | Significant | | | |
| | in Active | Other | Significant | | |
| | Markets for | Observable | Unobservable | | |
| | Identical Inputs | Inputs | Inputs | | |
| Millions | (Level 1) | (Level 2) | (Level 3) | Total | |
| Plan assets at fair value: | | | | | | | | | | | | | | | | |
| Temporary cash investments | | $ | 1 | | | $ | - | | | $ | - | | | $ | 1 | |
| Registered investment companies [a] | | | 6 | | | | - | | | | - | | | | 6 | |
| Federal government securities | | | - | | | | 803 | | | | - | | | | 803 | |
| Bonds and debentures | | | - | | | | 1,069 | | | | - | | | | 1,069 | |
| Corporate stock | | | 1,104 | | | | 7 | | | | - | | | | 1,111 | |
| Total plan assets at fair value | | $ | 1,111 | | | $ | 1,879 | | | $ | - | | | $ | 2,990 | |
| Plan assets at NAV: | | | | | | | | | | | | | | | | |
| Registered investment companies [b] | | | | | | | | | | | | | | | 68 | |
| Venture capital and buyout partnerships | | | | | | | | | | | | | | | 611 | |
| Real estate funds | | | | | | | | | | | | | | | 37 | |
| Collective trust and other funds | | | | | | | | | | | | | | | 622 | |
| Total plan assets at NAV | | | | | | | | | | | | | | $ | 1,338 | |
| Other assets/(liabilities) [c] | | | | | | | | | | | | | | | 35 | |
| Total plan assets | | | | | | | | | | | | | | $ | 4,363 | |
|