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Capital Stock - Stock Repurchases (Details) - Stock repurchase program - Class A common stock - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended |
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Sep. 30, 2025 | Dec. 31, 2024 | Dec. 31, 2011
Stock repurchases |  |  |
Amount of authorized stock repurchases approved for continuation under the current program |  |  | $ 150.0
Shares repurchased under stock repurchase program (in shares) | 0 | 0 |
Approximate amount of repurchase authority remaining under the current stock repurchase program | $ 17.8 |  |

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