Retirement Benefit and Other Post-retirement Obligations - Summary of Defined Plan Analysis (Detail) - UK Group plan [member] |
Dec. 31, 2025 |
|---|---|
| Disclosure of defined benefit plans [line items] | |
| Defined benefit | 47.00% |
| Defined contribution | 53.00% |
| Total | 100.00% |
| Active [member] | |
| Disclosure of defined benefit plans [line items] | |
| Defined benefit | 0.00% |
| Defined contribution | 11.00% |
| Total | 11.00% |
| Deferred [member] | |
| Disclosure of defined benefit plans [line items] | |
| Defined benefit | 12.00% |
| Defined contribution | 42.00% |
| Total | 54.00% |
| Pensioners [member] | |
| Disclosure of defined benefit plans [line items] | |
| Defined benefit | 35.00% |
| Defined contribution | 0.00% |
| Total | 35.00% |