Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions |
12 Months Ended | ||
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May 31, 2025 |
May 31, 2024 |
May 31, 2023 |
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| Unrealized gains (losses) on securities, tax | $ 26.4 | $ 2.6 | $ (12.2) |
| Reclassification adjustment for realized gains (losses) on securities, tax | $ 0.1 | $ (0.7) | $ 2.5 |
| Dividends declared, per share | $ 4.02 | $ 3.65 | $ 3.26 |
| Authorized In July 2021 [Member] | |||
| Expiration date | Jan. 31, 2024 | Jan. 31, 2024 | Jan. 31, 2024 |
| Authorized In January 2024 [Member] | |||
| Expiration date | May 31, 2027 | May 31, 2027 | May 31, 2027 |
| Maximum [Member] | Authorized In July 2021 [Member] | |||
| Approved repurchase amount | $ 400.0 | $ 400.0 | $ 400.0 |
| Maximum [Member] | Authorized In January 2024 [Member] | |||
| Approved repurchase amount | $ 400.0 | $ 400.0 | $ 400.0 |
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- Definition Amount authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Expiration date for purchase of share under share repurchase plan, in YYYY-MM-DD format. Includes, but is not limited to, repurchase of stock and unit of ownership. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Aggregate dividends declared during the period for each share of common stock outstanding. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, before adjustment, of tax expense (benefit) for unrealized holding gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes tax expense (benefit) for unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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