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Claim and Claim Adjustment Expense Reserves - Net Prior Year Development in CNA's Property and Casualty Operations (Detail) - CNA Financial [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Medical professional liability	$ 15	$ 20
Other professional liability and management liability	(12)	(34)
Surety	(25)	(15)
Commercial auto	(5)	(1)
General liability	(20)	(8)
Workers' compensation	2	(6)
Property and other	31	5
Total pretax (favorable) unfavorable development	$ (14)	$ (39)

X

- Definition

Net prior year claim and allocated claim adjustment.

+ References

No definition available.

+ Details

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- Definition

Net Prior Year Claim and Allocated Claim Adjustment Expense, Medical Professional Liability

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No definition available.

+ Details

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- Definition

Net Prior Year Claim And Allocated Claim Adjustment Expense Other Professional Liability And Management Liability

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No definition available.

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- Definition

Net Prior Year Claim and Allocated Claim Adjustment Expense, Property and Other.

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- Definition

Net prior year claim and allocated claim adjustment expense, surety.

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No definition available.

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- Definition

Net Prior Year Claim and Allocated Claim Adjustment, General Liability

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No definition available.

+ Details

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- Definition

Net Prior Year Claim and Allocated Claim Adjustment, Workers Compensation

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No definition available.

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- Definition

Pretax favorable unfavorable net prior year claim and allocated claim adjustment expense reserve development excluding life group.

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No definition available.

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- 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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