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Note 12 - Retirement Benefit Plans - Actuarial Gains (Losses), Benefit Cost, Cash Flows (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Interest cost | $ (8.7) | $ (6.7) | $ (16.5) | $ (13.5)
Amortization of prior service cost | (0.1) | (0.1) | (0.2) | (0.2)
Amortization of net gain | (0.6) | (0.3) | (1.1) | (0.6)
Expected return on plan assets | 8.7 | 6.5 | 16.4 | 13.4
Net periodic benefit cost | $ (0.7) | $ (0.6) | $ (1.4) | $ (0.9)

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