Legal Proceedings, Commitments and Contingencies, and Guarantees	12 Months Ended
Dec. 31, 2016
Legal Proceedings, Commitments and Contingencies, and Guarantees [Abstract]
Legal Proceedings, Commitments and Contingencies, and Guarantees [Text Block]	Note F. Legal Proceedings, Commitments and Contingencies, 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. Management has only recently begun evaluating the lawsuit as 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 December 31, 2016, 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 Contingency The Company recently identified rating errors related to its multi-peril package product within its Small Business unit. The Company recorded a charge which reduced Earned premium by $16 million in anticipation of voluntarily issuing $30 million of premium refunds related to affected policies written from December 1, 2015 through December 31, 2016. Earned premium in 2017 will be negatively impacted by the portion of the $30 million that has not yet been earned through December 31, 2016 and the expected refund amount will increase further because of premium written in 2017 prior to the Company’s actions to correct its rating process. The Company is currently in dialogue with state regulators and providing them with details regarding the anticipated premium refunds and other corrective actions. The Company is reviewing other business lines to determine whether other similar issues exist. Fines or penalties related to the foregoing or further refunds which may be required are reasonably possible, but the amount of such losses, if any, cannot be estimated at this time. 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 Consolidated Financial Statements. Commitments and Contingencies The Company holds an investment in a real estate joint venture in which the Company, on a joint and several basis with the other unrelated shareholders, guaranteed to fund operating deficits of the joint venture and an operating lease for an office building entered into by the venture. The lease was terminated in March 2016. In the event that the other parties to the joint venture are unable to meet their commitments in funding this joint venture, the Company would be required to assume future obligations, primarily related to the wind-down of the lease and joint venture. The Company does not believe it is likely that it will be required to do so. However, as of December 31, 2016, the maximum potential loss that the Company could be required to pay under this guarantee, in excess of amounts already recorded, was approximately $11 million. If the Company were required to assume future obligations, the Company would have the right to pursue reimbursement from the other shareholders. Guarantees As of December 31, 2016 and December 31, 2015, 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 a previously owned subsidiary 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, 2016, the aggregate amount related to quantifiable guarantees was $375 million and the aggregate amount related to quantifiable indemnification agreements was $258 million. Should the Company be required to make payments under the guarantee, it would have the right to seek reimbursement in certain cases 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 December 31, 2016, 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 December 31, 2016, the potential amount of future payments the Company could be required to pay under these guarantees was approximately $1.9 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.

Note F. Legal Proceedings, Commitments and Contingencies, 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. Management has only recently begun evaluating the lawsuit as 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 December 31, 2016, 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 Contingency

The Company recently identified rating errors related to its multi-peril package product within its Small Business unit. The Company recorded a charge which reduced Earned premium by $16 million in anticipation of voluntarily issuing $30 million of premium refunds related to affected policies written from December 1, 2015 through December 31, 2016. Earned premium in 2017 will be negatively impacted by the portion of the $30 million that has not yet been earned through December 31, 2016 and the expected refund amount will increase further because of premium written in 2017 prior to the Company’s actions to correct its rating process. The Company is currently in dialogue with state regulators and providing them with details regarding the anticipated premium refunds and other corrective actions. The Company is reviewing other business lines to determine whether other similar issues exist. Fines or penalties related to the foregoing or further refunds which may be required are reasonably possible, but the amount of such losses, if any, cannot be estimated at this time.

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 Consolidated Financial Statements.

Commitments and Contingencies

The Company holds an investment in a real estate joint venture in which the Company, on a joint and several basis with the other unrelated shareholders, guaranteed to fund operating deficits of the joint venture and an operating lease for an office building entered into by the venture. The lease was terminated in March 2016. In the event that the other parties to the joint venture are unable to meet their commitments in funding this joint venture, the Company would be required to assume future obligations, primarily related to the wind-down of the lease and joint venture. The Company does not believe it is likely that it will be required to do so. However, as of December 31, 2016, the maximum potential loss that the Company could be required to pay under this guarantee, in excess of amounts already recorded, was approximately $11 million. If the Company were required to assume future obligations, the Company would have the right to pursue reimbursement from the other shareholders.

Guarantees

As of December 31, 2016 and December 31, 2015, 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 a previously owned subsidiary 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, 2016, the aggregate amount related to quantifiable guarantees was $375 million and the aggregate amount related to quantifiable indemnification agreements was $258 million. Should the Company be required to make payments under the guarantee, it would have the right to seek reimbursement in certain cases 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 December 31, 2016, 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 December 31, 2016, the potential amount of future payments the Company could be required to pay under these guarantees was approximately $1.9 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.