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Dividends on common stock: (Details) - USD ($) $ / shares in Units, $ in Millions | 1 Months Ended | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Aug. 06, 2025 | Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Dividends on common stock |  |  |  |  |
Dividends declared per common share |  | $ 1.01 | $ 0.975 | $ 2.015 | $ 1.94
O 2025 Q3 Dividends | Subsequent Events |  |  |  |  |
Dividends on common stock |  |  |  |  |
Dividends, date of approval | Aug. 06, 2025 |  |  |  |
Dividends declared per common share | $ 1.015 |  |  |  |
Dividends payable | $ 48.4 |  |  |  |
Dividends payable date | Sep. 05, 2025 |  |  |  |

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