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Deposits (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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Deposits [Abstract] |  |
Time Deposits, $250,000 Or More | $ 758 | $ 523

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- Definition Time Deposits, $250,000 Or More + References No definition available. + Details
Name: | asb_TimeDeposits250000OrMore
Namespace Prefix: | asb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_DepositsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration