Commitments and Contingencies	12 Months Ended
Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 18. Commitments and Contingencies CNA Guarantees In the course of selling business entities and assets to third parties, CNA agreed to guarantee the performance of certain obligations of previously owned subsidiaries and to indemnify purchasers for losses arising out of breaches of representation and warranties with respect to the business entities or assets sold, including, in certain cases, losses arising from undisclosed liabilities or certain named litigation. Such guarantee and indemnification agreements in effect for sales of business entities, assets and third party loans may include provisions that survive indefinitely. As of December 31, 2017, the aggregate amount related to quantifiable guarantees was $375 million and the aggregate amount related to quantifiable indemnification agreements was $252 million. In certain cases, should CNA be required to make payments under any such guarantee, it would have the right to seek reimbursement from an affiliate of a previously owned subsidiary. In addition, CNA has agreed to provide indemnification to third party purchasers for certain losses associated with sold business entities or assets that are not limited by a contractual monetary amount. As of December 31, 2017, CNA had outstanding unlimited indemnifications in connection with the sales of certain of its business entities or assets that included tax liabilities arising prior to a purchaser’s ownership of an entity or asset, defects in title at the time of sale, employee claims arising prior to closing and in some cases losses arising from certain litigation and undisclosed liabilities. Certain provisions of the indemnification agreements survive indefinitely while others survive until the applicable statutes of limitation expire, or until the agreed upon contract terms expire. CNA also provided guarantees, if the primary obligor fails to perform, to holders of structured settlement annuities provided by a previously owned subsidiary. As of December 31, 2017, the potential amount of future payments CNA could be required to pay under these guarantees was approximately $1.8 billion, which will be paid over the lifetime of the annuitants. CNA does not believe any payment is likely under these guarantees, as CNA is the beneficiary of a trust that must be maintained at a level that approximates the discounted reserves for these annuities. CNA Small Business Premium Rate Adjustment In 2016 and 2017, CNA identified rating errors related to its multi-peril package product and workers’ compensation policies within its Small Business unit and determined that it would voluntarily issue premium refunds along with interest on affected policies. After the rating errors were identified, written and earned premium have been reported net of any impact from the premium rate adjustments. For the year ended December 31, 2017, CNA recognized $36 million of adverse premium development and also increased interest expense by $7 million for interest due to policyholders on the premium rate adjustments. For the year ended December 31, 2016 CNA recorded a charge which reduced earned premium by $16 million. The policyholder refunds for the multi-peril package product were issued in the third quarter of 2017. The policyholder refunds for workers’ compensation policies are expected to be refunded in 2018. The estimated refund liability, including interest, for the workers’ compensation policies as of December 31, 2017 was $60 million. Any fines or penalties related to the foregoing are reasonably possible, but are not expected to be material to the Company’s financial statements.

Note 18. Commitments and Contingencies

CNA Guarantees

In the course of selling business entities and assets to third parties, CNA agreed to guarantee the performance of certain obligations of previously owned subsidiaries and to indemnify purchasers for losses arising out of breaches of representation and warranties with respect to the business entities or assets sold, including, in certain cases, losses arising from undisclosed liabilities or certain named litigation. Such guarantee and indemnification agreements in effect for sales of business entities, assets and third party loans may include provisions that survive indefinitely. As of December 31, 2017, the aggregate amount related to quantifiable guarantees was $375 million and the aggregate amount related to quantifiable indemnification agreements was $252 million. In certain cases, should CNA be required to make payments under any such guarantee, it would have the right to seek reimbursement from an affiliate of a previously owned subsidiary.

In addition, CNA has agreed to provide indemnification to third party purchasers for certain losses associated with sold business entities or assets that are not limited by a contractual monetary amount. As of December 31, 2017, CNA had outstanding unlimited indemnifications in connection with the sales of certain of its business entities or assets that included tax liabilities arising prior to a purchaser’s ownership of an entity or asset, defects in title at the time of sale, employee claims arising prior to closing and in some cases losses arising from certain litigation and undisclosed liabilities. Certain provisions of the indemnification agreements survive indefinitely while others survive until the applicable statutes of limitation expire, or until the agreed upon contract terms expire.

CNA also provided guarantees, if the primary obligor fails to perform, to holders of structured settlement annuities provided by a previously owned subsidiary. As of December 31, 2017, the potential amount of future payments CNA could be required to pay under these guarantees was approximately $1.8 billion, which will be paid over the lifetime of the annuitants. CNA does not believe any payment is likely under these guarantees, as CNA is the beneficiary of a trust that must be maintained at a level that approximates the discounted reserves for these annuities.

CNA Small Business Premium Rate Adjustment

In 2016 and 2017, CNA identified rating errors related to its multi-peril package product and workers’ compensation policies within its Small Business unit and determined that it would voluntarily issue premium refunds along with interest on affected policies. After the rating errors were identified, written and earned premium have been reported net of any impact from the premium rate adjustments. For the year ended December 31, 2017, CNA recognized $36 million of adverse premium development and also increased interest expense by $7 million for interest due to policyholders on the premium rate adjustments. For the year ended December 31, 2016 CNA recorded a charge which reduced earned premium by $16 million.

The policyholder refunds for the multi-peril package product were issued in the third quarter of 2017. The policyholder refunds for workers’ compensation policies are expected to be refunded in 2018. The estimated refund liability, including interest, for the workers’ compensation policies as of December 31, 2017 was $60 million. Any fines or penalties related to the foregoing are reasonably possible, but are not expected to be material to the Company’s financial statements.