Tax - Schedule of Income Tax Expense (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Current: | |||
| United Kingdom | $ 138.3 | $ 145.8 | $ 93.4 |
| Foreign Other | 20.7 | 21.9 | 18.6 |
| Total Current | 159.0 | 167.7 | 112.0 |
| Deferred: | |||
| United Kingdom | 0.6 | (0.7) | 40.7 |
| Foreign Other | 2.1 | 0.2 | 2.5 |
| Total Deferred | 2.7 | (0.5) | 43.2 |
| Tax (benefit)/expense | $ 161.7 | $ 167.2 | $ 155.2 |
| X | ||||||||||
- Definition Amount of current federal, state, and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current national, regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Amount of current foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of deferred federal, state, and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, deferred national, regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of deferred foreign income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|