Retirement Benefit and Other Post-retirement Obligations - Summary of Liquidity Profile of UK Group Plan Assets (Detail) - UK Group plan [member] |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Later than one month and not later than three months [member] | ||
| Disclosure of liquidity profile [line items] | ||
| Liquidity percentage of plan asset | 2.00% | 2.00% |
| Later than 3 months [member] | ||
| Disclosure of liquidity profile [line items] | ||
| Liquidity percentage of plan asset | 45.00% | 48.00% |
| Not later than 1 month [member] | ||
| Disclosure of liquidity profile [line items] | ||
| Liquidity percentage of plan asset | 53.00% | 50.00% |