Reinsurance and Indemnification - Kentucky Earthquake Excess Catastrophe Reinsurance Contract (Details) - Kentucky Agreement $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Reinsurance Retention Policy [Line Items]
Term of catastrophe reinsurance agreement contract	3 years
Limit of aggregate losses under aggregate excess agreement	$ 28
Retention percentage of reinsurance limit	95.00%
Retention amount for catastrophe reinsurance agreement contracts	$ 2

- Definition

Represents the retention percentage of annual coverage limit provided by the insurance arrangement for catastrophe claims.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The limit of aggregated losses per contract year beyond which coverage provided by an aggregate excess agreement applies.

+ References

No definition available.

+ Details

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Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the period of catastrophe reinsurance agreement contract.

+ References

No definition available.

+ Details

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Namespace Prefix:	all_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the retention amount of catastrophe reinsurance agreement contracts.

+ References

No definition available.

+ Details

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Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Details

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