Legal Proceedings and Guarantees	3 Months Ended
Mar. 31, 2017
Legal Proceedings, Commitments and Contingencies, and Guarantees [Abstract]
Legal Proceedings and Guarantees	Legal Proceedings and Guarantees CNA 401(k) Plus Plan Litigation In September 2016, a class action lawsuit was filed against CCC, Continental Assurance Company (CAC), CNAF, the Investment Committee of the CNA 401(k) Plus Plan, The Northern Trust Company and John Does 1-10 (collectively Defendants) over the CNA 401(k) Plus Plan. The complaint alleges that Defendants breached fiduciary duties to the CNA 401(k) Plus Plan and caused prohibited transactions in violation of the Employee Retirement Income Security Act of 1974 when the CNA 401(k) Plus Plan's Fixed Income Fund’s annuity contract with CAC was canceled. The plaintiff alleges he and a proposed class of the CNA 401(k) Plus Plan participants who had invested in the Fixed Income Fund suffered lower returns in their CNA 401(k) Plus Plan investments as a consequence of these alleged violations and seeks relief on behalf of the putative class. This litigation is in its preliminary stages, and as of yet no class has been certified. CCC and the other defendants are contesting the case and management currently is unable to predict the final outcome or the impact on the Company’s financial condition, results of operations, or cash flows. As of March 31, 2017, the likelihood of loss is reasonably possible, but the amount of loss, if any, cannot be estimated at this stage of the litigation. Small Business Premium Rate Adjustment The Company identified rating errors related to its multi-peril package product within its Small Business unit in the fourth quarter of 2016 and recorded a charge which reduced Earned premium by $16 million in anticipation of voluntarily issuing premium refunds related to affected policies written from December 1, 2015. The Company notified state regulators and provided them with details regarding these anticipated voluntary premium refunds and other corrective actions related to the multi-peril package product. At that time, the Company also alerted regulators that it was reviewing other business lines to determine whether similar issues exist. In the first quarter of 2017, the Company concluded its review and determined that there were also rating errors related to Small Business workers' compensation policies. Accordingly, the Company recorded a charge which reduced Earned premium by $42 million in anticipation of voluntarily issuing premium refunds related to affected policies written from March 1, 2014. The Company is currently in dialogue with state regulators regarding this matter. The estimated refund liability for the multi-peril product and workers' compensations policies as of March 31, 2017 was $36 million and $50 million, respectively. In the first quarter of 2017, the Company also recorded a $5 million liability for interest due to policyholders on the aggregate refund amounts. Any fines or penalties related to the foregoing are reasonably possible, but are not expected to be material to the Company's Condensed Consolidated Financial Statements. The amount of the refund and corresponding liability will continue to increase until required changes to the automated rating processes are fully implemented. The changes are expected to be implemented by the end of May for the multi-peril product and by the end of September for workers' compensation policies. Accordingly, subsequent to the periods discussed in the preceding paragraphs, written and earned premium for the subject product and policy lines are reported net of any impact from the premium rate adjustments. Other Litigation The Company is a party to other routine litigation incidental to its business, which, based on the facts and circumstances currently known, is not material to the Condensed Consolidated Financial Statements. Guarantees As of March 31, 2017 and December 31, 2016, the Company had recorded liabilities of approximately $5 million related to guarantee and indemnification agreements. Management believes that it is not likely that any future indemnity claims will be significantly greater than the amounts recorded. In the course of selling business entities and assets to third parties, the Company agreed to guarantee the performance of certain obligations of previously owned subsidiaries and to indemnify purchasers for losses arising out of breaches of representations 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 March 31, 2017, the aggregate amount related to quantifiable guarantees was $434 million and the aggregate amount related to quantifiable indemnification agreements was $254 million. In certain cases, should the Company 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, the Company 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 March 31, 2017, the Company 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. The Company also provided guarantees, if the primary obligor fails to perform, to holders of structured settlement annuities provided by a previously owned subsidiary. As of March 31, 2017, the potential amount of future payments the Company could be required to pay under these guarantees was approximately $1.8 billion, which will be paid over the lifetime of the annuitants. The Company does not believe any payment is likely under these guarantees, as the Company is the beneficiary of a trust that must be maintained at a level that approximates the discounted reserves for these annuities.

Legal Proceedings and Guarantees

CNA 401(k) Plus Plan Litigation

In September 2016, a class action lawsuit was filed against CCC, Continental Assurance Company (CAC), CNAF, the Investment Committee of the CNA 401(k) Plus Plan, The Northern Trust Company and John Does 1-10 (collectively Defendants) over the CNA 401(k) Plus Plan. The complaint alleges that Defendants breached fiduciary duties to the CNA 401(k) Plus Plan and caused prohibited transactions in violation of the Employee Retirement Income Security Act of 1974 when the CNA 401(k) Plus Plan's Fixed Income Fund’s annuity contract with CAC was canceled. The plaintiff alleges he and a proposed class of the CNA 401(k) Plus Plan participants who had invested in the Fixed Income Fund suffered lower returns in their CNA 401(k) Plus Plan investments as a consequence of these alleged violations and seeks relief on behalf of the putative class. This litigation is in its preliminary stages, and as of yet no class has been certified. CCC and the other defendants are contesting the case and management currently is unable to predict the final outcome or the impact on the Company’s financial condition, results of operations, or cash flows. As of March 31, 2017, the likelihood of loss is reasonably possible, but the amount of loss, if any, cannot be estimated at this stage of the litigation.

Small Business Premium Rate Adjustment

The Company identified rating errors related to its multi-peril package product within its Small Business unit in the fourth quarter of 2016 and recorded a charge which reduced Earned premium by $16 million in anticipation of voluntarily issuing premium refunds related to affected policies written from December 1, 2015. The Company notified state regulators and provided them with details regarding these anticipated voluntary premium refunds and other corrective actions related to the multi-peril package product. At that time, the Company also alerted regulators that it was reviewing other business lines to determine whether similar issues exist.

In the first quarter of 2017, the Company concluded its review and determined that there were also rating errors related to Small Business workers' compensation policies. Accordingly, the Company recorded a charge which reduced Earned premium by $42 million in anticipation of voluntarily issuing premium refunds related to affected policies written from March 1, 2014. The Company is currently in dialogue with state regulators regarding this matter.

The estimated refund liability for the multi-peril product and workers' compensations policies as of March 31, 2017 was $36 million and $50 million, respectively. In the first quarter of 2017, the Company also recorded a $5 million liability for interest due to policyholders on the aggregate refund amounts. Any fines or penalties related to the foregoing are reasonably possible, but are not expected to be material to the Company's Condensed Consolidated Financial Statements.

The amount of the refund and corresponding liability will continue to increase until required changes to the automated rating processes are fully implemented. The changes are expected to be implemented by the end of May for the multi-peril product and by the end of September for workers' compensation policies. Accordingly, subsequent to the periods discussed in the preceding paragraphs, written and earned premium for the subject product and policy lines are reported net of any impact from the premium rate adjustments.

Other Litigation

The Company is a party to other routine litigation incidental to its business, which, based on the facts and circumstances currently known, is not material to the Condensed Consolidated Financial Statements.

Guarantees

As of March 31, 2017 and December 31, 2016, the Company had recorded liabilities of approximately $5 million related to guarantee and indemnification agreements. Management believes that it is not likely that any future indemnity claims will be significantly greater than the amounts recorded.

In the course of selling business entities and assets to third parties, the Company agreed to guarantee the performance of certain obligations of previously owned subsidiaries and to indemnify purchasers for losses arising out of breaches of representations 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 March 31, 2017, the aggregate amount related to quantifiable guarantees was $434 million and the aggregate amount related to quantifiable indemnification agreements was $254 million. In certain cases, should the Company 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, the Company 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 March 31, 2017, the Company 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.

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