Consolidated Statements of Stockholders' Equity (USD $) In Millions, unless otherwise specified
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Total
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Common stock [Member]
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Additional paid-in capital [Member]
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Retained earnings [Member]
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Accumulated other comprehensive income (loss) [Member]
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Treasury stock [Member]
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Notes receivable for the issuance of common stock [Member]
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Balance at Dec. 31, 2011 |
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$ 683us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |
$ 2,141us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
$ 8,308us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
$ 480us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
$ (102)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
$ (22)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |
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Net income (loss) |
628us-gaap_NetIncomeLoss |
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628us-gaap_NetIncomeLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Other comprehensive income (loss), net of tax |
351us-gaap_OtherComprehensiveIncomeLossNetOfTax |
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351us-gaap_OtherComprehensiveIncomeLossNetOfTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
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Dividends paid to common stockholders |
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(162)us-gaap_DividendsCommonStockCash / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Stock-based compensation |
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5cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
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3cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
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(Decrease) increase in notes receivable from the issuance of common stock |
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1cna_Decreaseincreaseinnotesreceivableforcommonstock / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Balance at Dec. 31, 2012 |
12,314us-gaap_StockholdersEquity |
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683us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |
2,146us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
8,774us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
831us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
(99)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
(21)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |
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Net income (loss) |
937us-gaap_NetIncomeLoss |
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937us-gaap_NetIncomeLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Other comprehensive income (loss), net of tax |
(389)us-gaap_OtherComprehensiveIncomeLossNetOfTax |
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(389)us-gaap_OtherComprehensiveIncomeLossNetOfTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
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Dividends paid to common stockholders |
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(216)us-gaap_DividendsCommonStockCash / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Stock-based compensation |
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(1)cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
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8cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
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(Decrease) increase in notes receivable from the issuance of common stock |
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(2)cna_Decreaseincreaseinnotesreceivableforcommonstock / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Balance at Dec. 31, 2013 |
12,651us-gaap_StockholdersEquity |
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683us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |
2,145us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
9,495us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
442us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
(91)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
(23)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Increase (Decrease) in Stockholders' Equity [Roll Forward] |
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Net income (loss) |
691us-gaap_NetIncomeLoss |
[1] |
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691us-gaap_NetIncomeLoss / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Other comprehensive income (loss), net of tax |
(42)us-gaap_OtherComprehensiveIncomeLossNetOfTax |
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(42)us-gaap_OtherComprehensiveIncomeLossNetOfTax / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
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Dividends paid to common stockholders |
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(541)us-gaap_DividendsCommonStockCash / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
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Stock-based compensation |
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6cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
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7cna_StockBasedCompensation / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
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(Decrease) increase in notes receivable from the issuance of common stock |
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22cna_Decreaseincreaseinnotesreceivableforcommonstock / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
Balance at Dec. 31, 2014 |
$ 12,794us-gaap_StockholdersEquity |
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$ 683us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember |
$ 2,151us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AdditionalPaidInCapitalMember |
$ 9,645us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_RetainedEarningsMember |
$ 400us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherComprehensiveIncomeMember |
$ (84)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = us-gaap_TreasuryStockMember |
$ (1)us-gaap_StockholdersEquity / us-gaap_StatementEquityComponentsAxis = cna_NotesReceivableForIssuanceOfCommonStockMember |
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