Subsequent Event (Details) - Wildfire [Member] - Subsequent Event [Member] $ in Millions	Oct. 15, 2017 USD ($) structure
Subsequent Event [Line Items]
Structures destroyed \| structure	100
Reinsurance recoverables	$ 10
Reinstatement premium, maximum	19
Minimum [Member]
Subsequent Event [Line Items]
Pre-tax catastrophe losses	60
Maximum [Member]
Subsequent Event [Line Items]
Pre-tax catastrophe losses	$ 100
Reinsurance Policy, Up To Two Hundred Million [Member]
Subsequent Event [Line Items]
Reinsurance retention policy, reinsured risk, percentage	100.00%
Reinsurance retention policy, excess retention, amount reinsured	$ 190
Reinsurance retention policy, retention	$ 10
Reinsurance Policy, Above Two Hundred Million [Member]
Subsequent Event [Line Items]
Reinsurance retention policy, reinsured risk, percentage	5.00%
Reinsurance retention policy, retention	$ 15
Reinsurance retention policy, lower limit	$ 200
Reinsurance retention policy, retention, percentage	95.00%
Northern California
Subsequent Event [Line Items]
Structures destroyed \| structure	8,000

Reinsurance Retention Policy, Lower Limit

No definition available.

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- Definition

Unusual or Infrequent Item, Structures Destroyed

+ References

No definition available.

+ Details

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- Definition

The amount of estimated liability as of the balance sheet date for the specific conflagration, earthquake, windstorm, explosion, or similar event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437

+ Details

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- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

No definition available.

+ Details

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- Definition

Amount before valuation allowance of reinsurance recoverables for losses reported to the ceding insurer but not yet paid, and for amounts expected based upon statistical projections and other measures of incurred losses and loss settlement expenses which have not yet been reported to the ceding insurer.

+ References

No definition available.

+ Details

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- Definition

Stated amount that is the upper retention limit per entity policy.

+ References

No definition available.

+ Details

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- Definition

Amount of risk reinsured in excess of stated retention per company policy.

+ References

No definition available.

+ Details

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- Definition

Percentage of risk reinsured in excess of stated retention per entity policy.

+ References

No definition available.

+ Details

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- Definition

Percentage of risk reinsured on insurance products per entity policy.

+ References

No definition available.

+ Details

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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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