Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Jan. 19, 2024 |
Feb. 29, 2024 |
Feb. 28, 2023 |
Feb. 29, 2024 |
Feb. 28, 2023 |
|
| Unrealized gains (losses) on securities, tax | $ 6.3 | $ (3.3) | $ 3.5 | $ (23.3) | |
| Reclassification adjustment for realized gains (loss) on securities, tax | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0 | |
| Cash dividends declared, per share | $ 0.89 | $ 0.79 | $ 2.67 | $ 2.37 | |
| Authorized In January 2024 [Member] | |||||
| Expiration date | Jan. 31, 2024 | ||||
| Authorized In January 2024 [Member] | Maximum [Member] | |||||
| Approved repurchase amount | $ 400.0 | $ 400.0 | |||
| Authorized In January 19 2024 [Member] | |||||
| Expiration date | May 31, 2027 | ||||
| Authorized In January 19 2024 [Member] | Maximum [Member] | |||||
| Approved repurchase amount | $ 400.0 | ||||