| **Schedule II. Condensed Financial Information of Registrant (Parent Company) Schedule II. Condensed Financial Information of Registrant (Parent Company)** | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
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| **Condensed Financial Information of Parent Company Only Disclosure [Abstract]**                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Condensed Statement of Comprehensive Income [Table Text Block]                                                                                              | CNA Financial CorporationStatements of Operations and Comprehensive (Loss) IncomeYears ended December 31     (In millions)2015 2014 2013Revenues     Net investment income$1 $1 $1Net realized investment gains 5 4 4Total revenues6 5 5Expenses     Administrative and general1 5 (7)Interest154 182 165Total expenses155 187 158Loss from operations before income taxes and equity in net income of subsidiaries(149) (182) (153)Income tax benefit 34 35 22Loss before equity in net income of subsidiaries(115) (147) (131)Equity in net income of subsidiaries594 838 1,068Net income479 691 937Equity in other comprehensive income of subsidiaries(715) (42) (389)Total Comprehensive (Loss) Income$(236) $649 $548                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Condensed Balance Sheet [Table Text Block]                                                                                                                  | CNA Financial CorporationBalance SheetsDecember 31   (In millions, except share data)2015 2014Assets   Investment in subsidiaries$13,851 $14,867Cash4 1Fixed maturity securities available-for-sale, at fair value (amortized cost of $0 and $1)— 1Short term investments478 499Other assets3 3Total assets$14,336 $15,371Liabilities   Short term debt$350 $—Long term debt2,182 2,529Other liabilities48 48Total liabilities2,580 2,577Stockholders' Equity   Common stock ($2.50 par value; 500,000,000 shares authorized; 273,040,243 shares issued;  270,274,361 and 269,980,202 shares outstanding)683 683Additional paid-in capital2,153 2,151Retained earnings9,313 9,645Accumulated other comprehensive income(315) 400Treasury stock (2,765,882 and 3,060,041 shares), at cost(78) (84)Notes receivable for the issuance of common stock— (1)Total stockholders' equity11,756 12,794Total liabilities and stockholders' equity$14,336 $15,371                                                                                                                                                                                                                                                                                                                                                                                                                       |
| Condensed Cash Flow Statement [Table Text Block]                                                                                                            | CNA Financial CorporationStatements of Cash FlowsYears ended December 31     (In millions)2015 2014 2013Cash Flows from Operating Activities     Net income$479 $691 $937Adjustments to reconcile net income to net cash flows provided by operating activities:     Equity in net income of subsidiaries(594) (838) (1,068)Dividends received from subsidiaries900 650 400Net realized investment gains(5) (4) (4)Other, net4 14 8Total adjustments305 (178) (664)Net cash flows provided by operating activities784 513 273Cash Flows from Investing Activities     Proceeds from fixed maturity securities— — 1Change in short term investments21 6 (57)Capital contributions to subsidiaries— (10) (12)Other, net7 5 4Net cash flows provided (used) by investing activities28 1 (64)Cash Flows from Financing Activities     Dividends paid to common stockholders(811) (541) (216)Proceeds from the issuance of debt— 546 —Repayment of debt— (549) (3)Stock options exercised1 5 2Other, net1 25 9Net cash flows used by financing activities(809) (514) (208)Net change in cash3 — 1Cash, beginning of year1 1 —Cash, end of year$4 $1 $1 |

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Tabular disclosure of condensed statement of comprehensive income (loss) including, but not limited to, statements of comprehensive income (loss) of consolidated entities and consolidation eliminations.
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Tabular disclosure of condensed balance sheet, including, but not limited to, balance sheets of consolidated entities and consolidation eliminations.
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| - Definition
Tabular disclosure of condensed cash flow statement, including, but not limited to, cash flow statements of consolidated entities and consolidation eliminations.
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