Retirement Benefits (Details) - USD ($) |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2026 |
|
| Pension Plans | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | $ 69,000,000 | $ 66,000,000 | $ 138,000,000 | $ 132,000,000 | |
| Interest cost | 161,000,000 | 166,000,000 | 323,000,000 | 332,000,000 | |
| Expected return on plan assets | (322,000,000) | (320,000,000) | (644,000,000) | (640,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | 0 | 0 | |
| Regulatory asset | 0 | 0 | 0 | ||
| Net (gain) loss | 19,000,000 | 10,000,000 | 37,000,000 | 19,000,000 | |
| Net periodic pension income | (73,000,000) | (78,000,000) | (146,000,000) | (157,000,000) | |
| Pension Plans | Scenario, Forecast | |||||
| Defined Benefit Plan Disclosure [Line Items] | |||||
| Defined benefit plan, expected future employer contributions, remainder of fiscal year | $ 0 | ||||
| Pension Plans | ALABAMA POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 16,000,000 | 15,000,000 | 31,000,000 | 30,000,000 | |
| Interest cost | 37,000,000 | 38,000,000 | 75,000,000 | 77,000,000 | |
| Expected return on plan assets | (78,000,000) | (78,000,000) | (157,000,000) | (156,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | 0 | 0 | |
| Regulatory asset | 0 | 0 | 0 | ||
| Net (gain) loss | 5,000,000 | 4,000,000 | 10,000,000 | 6,000,000 | |
| Net periodic pension income | (20,000,000) | (21,000,000) | (41,000,000) | (43,000,000) | |
| Pension Plans | GEORGIA POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 16,000,000 | 15,000,000 | 33,000,000 | 31,000,000 | |
| Interest cost | 47,000,000 | 49,000,000 | 94,000,000 | 98,000,000 | |
| Expected return on plan assets | (100,000,000) | (99,000,000) | (199,000,000) | (198,000,000) | |
| Amortization: | |||||
| Prior service costs | 1,000,000 | 1,000,000 | 1,000,000 | 1,000,000 | |
| Regulatory asset | 0 | 0 | 0 | ||
| Net (gain) loss | 7,000,000 | 3,000,000 | 13,000,000 | 7,000,000 | |
| Net periodic pension income | (29,000,000) | (31,000,000) | (58,000,000) | (61,000,000) | |
| Pension Plans | MISSISSIPPI POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 3,000,000 | 2,000,000 | 6,000,000 | 5,000,000 | |
| Interest cost | 8,000,000 | 8,000,000 | 15,000,000 | 15,000,000 | |
| Expected return on plan assets | (14,000,000) | (14,000,000) | (29,000,000) | (29,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | 0 | 0 | |
| Regulatory asset | 0 | 0 | 0 | ||
| Net (gain) loss | 0 | 0 | 1,000,000 | 1,000,000 | |
| Net periodic pension income | (3,000,000) | (4,000,000) | (7,000,000) | (8,000,000) | |
| Pension Plans | SOUTHERN POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 1,000,000 | 2,000,000 | 3,000,000 | 3,000,000 | |
| Interest cost | 3,000,000 | 3,000,000 | 5,000,000 | 5,000,000 | |
| Expected return on plan assets | (4,000,000) | (4,000,000) | (8,000,000) | (8,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | 0 | 0 | |
| Regulatory asset | 0 | 0 | 0 | ||
| Net (gain) loss | (1,000,000) | (2,000,000) | (1,000,000) | (1,000,000) | |
| Net periodic pension income | (1,000,000) | (1,000,000) | (1,000,000) | (1,000,000) | |
| Pension Plans | SOUTHERN Co GAS | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 7,000,000 | 7,000,000 | 14,000,000 | 13,000,000 | |
| Interest cost | 11,000,000 | 11,000,000 | 22,000,000 | 22,000,000 | |
| Expected return on plan assets | (22,000,000) | (22,000,000) | (43,000,000) | (43,000,000) | |
| Amortization: | |||||
| Prior service costs | (1,000,000) | (1,000,000) | (1,000,000) | (1,000,000) | |
| Regulatory asset | 4,000,000 | 3,000,000 | 8,000,000 | ||
| Net (gain) loss | 1,000,000 | 0 | 1,000,000 | 0 | |
| Net periodic pension income | (4,000,000) | (1,000,000) | (4,000,000) | (1,000,000) | |
| Postretirement Benefits | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 3,000,000 | 3,000,000 | 6,000,000 | 6,000,000 | |
| Interest cost | 16,000,000 | 18,000,000 | 32,000,000 | 35,000,000 | |
| Expected return on plan assets | (22,000,000) | (22,000,000) | (45,000,000) | (45,000,000) | |
| Amortization: | |||||
| Prior service costs | 1,000,000 | 1,000,000 | |||
| Regulatory asset | 0 | 0 | |||
| Net (gain) loss | (2,000,000) | (4,000,000) | (4,000,000) | (7,000,000) | |
| Net periodic pension income | (5,000,000) | (5,000,000) | (10,000,000) | (10,000,000) | |
| Postretirement Benefits | ALABAMA POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 1,000,000 | 1,000,000 | 2,000,000 | 2,000,000 | |
| Interest cost | 4,000,000 | 4,000,000 | 8,000,000 | 8,000,000 | |
| Expected return on plan assets | (8,000,000) | (9,000,000) | (17,000,000) | (18,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | |||
| Regulatory asset | 0 | 0 | |||
| Net (gain) loss | (1,000,000) | 0 | (1,000,000) | 0 | |
| Net periodic pension income | (4,000,000) | (4,000,000) | (8,000,000) | (8,000,000) | |
| Postretirement Benefits | GEORGIA POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 1,000,000 | 1,000,000 | 2,000,000 | 2,000,000 | |
| Interest cost | 6,000,000 | 7,000,000 | 12,000,000 | 13,000,000 | |
| Expected return on plan assets | (8,000,000) | (8,000,000) | (16,000,000) | (16,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | |||
| Regulatory asset | 0 | 0 | |||
| Net (gain) loss | 0 | (2,000,000) | 0 | (2,000,000) | |
| Net periodic pension income | (1,000,000) | (2,000,000) | (2,000,000) | (3,000,000) | |
| Postretirement Benefits | MISSISSIPPI POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 0 | 0 | 0 | 0 | |
| Interest cost | 0 | 0 | 1,000,000 | 1,000,000 | |
| Expected return on plan assets | 1,000,000 | 0 | 0 | 0 | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | |||
| Regulatory asset | 0 | 0 | |||
| Net (gain) loss | 0 | 1,000,000 | 0 | 0 | |
| Net periodic pension income | 1,000,000 | 1,000,000 | 1,000,000 | 1,000,000 | |
| Postretirement Benefits | SOUTHERN POWER CO | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 0 | 0 | 0 | 0 | |
| Interest cost | 0 | 0 | 0 | 0 | |
| Expected return on plan assets | 0 | 0 | 0 | 0 | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | |||
| Regulatory asset | 0 | 0 | |||
| Net (gain) loss | 0 | 0 | 0 | 0 | |
| Net periodic pension income | 0 | 0 | 0 | 0 | |
| Postretirement Benefits | SOUTHERN Co GAS | |||||
| Pension Plans and Postretirement Plans | |||||
| Service cost | 0 | 0 | 0 | 0 | |
| Interest cost | 2,000,000 | 2,000,000 | 3,000,000 | 4,000,000 | |
| Expected return on plan assets | (2,000,000) | (2,000,000) | (4,000,000) | (4,000,000) | |
| Amortization: | |||||
| Prior service costs | 0 | 0 | |||
| Regulatory asset | 2,000,000 | 3,000,000 | |||
| Net (gain) loss | (2,000,000) | (2,000,000) | (4,000,000) | (4,000,000) | |
| Net periodic pension income | $ (2,000,000) | $ 0 | $ (5,000,000) | $ (1,000,000) | |