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Derivative Financial Instruments - Narrative (Details) | 9 Months Ended
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Sep. 30, 2021 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract] |
Potential recoveries | $ 0

X
- Definition Represents the potential amount of recoveries under sale of credit protection. + References No definition available. + Details
Name: | all_PotentialRecoveriesUnderCreditRiskDerivatives
Namespace Prefix: | all_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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