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Acquisitions (Detail) $ / shares in Units, $ in Millions |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 14, 2016 USD ($) $ / shares shares | Dec. 31, 2017 USD ($) shares | Dec. 31, 2016 USD ($) $ / shares shares | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) $ / shares shares | Apr. 01, 2015 USD ($) | Dec. 31, 2014 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted Average Number of Shares Outstanding, Basic | shares |  |  | 467,145,716 |  | 462,519,789 |  |  |  | 325,589,361 |  |  |  |
Cash |  |  | $ 728 | [1],[2] | $ 985 | [1],[3],[4] | $ 985 | [1],[3],[4] | $ 1,775 | [1],[5] |  | $ 655 | [5]
Investments |  |  | 102,444 |  | 99,094 |  | 99,094 |  |  |  |  |  |
Accrued investment income |  |  | 909 |  | 918 |  | 918 |  |  |  |  |  |
Insurance and reinsurance balances receivable |  |  | 9,334 |  | 8,970 |  | 8,970 |  |  |  |  |  |
Reinsurance recoverable on paid losses and loss expenses | [6] |  | 15,034 |  | 13,577 |  | 13,577 |  |  |  |  |  |
Prepaid reinsurance premiums |  |  | 2,529 |  | 2,448 |  | 2,448 |  |  |  |  |  |
Other assets |  |  | 6,358 |  | 5,090 |  | 5,090 |  |  |  |  |  |
Unpaid losses and loss expenses |  |  | (63,179) |  | (60,540) |  | (60,540) |  | (37,303) |  |  | $ (38,315) |
Unearned premiums |  |  | (15,216) |  | (14,779) |  | (14,779) |  |  |  |  |  |
Reinsurance Payable |  |  | (5,868) |  | (5,637) |  | (5,637) |  |  |  |  |  |
Accounts Payable, Accrued Expenses and Other Liabilities |  |  | (9,545) |  | (8,617) |  | (8,617) |  |  |  |  |  |
Deferred Tax Liabilities, Net |  |  | (699) |  | (988) |  | (988) |  |  |  |  |  |
Long-term Debt |  |  | (11,556) |  | (12,610) |  | (12,610) |  |  |  |  |  |
Intangible Assets, Net (Excluding Goodwill) |  |  | 6,513 |  | 6,763 |  | 6,763 |  |  |  |  |  |
Goodwill |  |  | 15,541 |  | 15,332 |  | 15,332 |  | 4,796 |  |  |  |
Common Shares (CHF 24.15 par value; 479,783,864 shares issued; 463,833,179 and 465,968,716 shares outstanding) |  |  | $ 11,121 |  | 11,121 |  | 11,121 |  |  |  |  |  |
Fireman's Fund high net worth personal lines [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Financing Of Acquisition With Cash |  |  |  |  |  |  |  |  |  |  | $ 365 |  |
Cash |  |  |  |  |  |  |  |  |  |  | 629 |  |
Insurance and reinsurance balances receivable |  |  |  |  |  |  |  |  |  |  | 124 |  |
Unpaid losses and loss expenses |  |  |  |  |  |  |  |  |  |  | (417) |  |
Unearned premiums |  |  |  |  |  |  |  |  |  |  | (428) |  |
Fair Value of Assets Acquired |  |  |  |  |  |  |  |  |  |  | 753 |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities |  |  |  |  |  |  |  |  |  |  | 863 |  |
Intangible Assets, Net (Excluding Goodwill) |  |  |  |  |  |  |  |  |  |  | 278 |  |
Goodwill |  |  |  |  |  |  |  |  |  |  | $ 196 |  |
The Chubb Corporation [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Total Value of Equity Awards Issued in Acquisition |  | $ 525 |  |  |  |  |  |  |  |  |  |  |
Purchase Price |  | 29,500 |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Financing Of Acquisition With Cash |  | 9,000 |  |  |  |  |  |  |  |  |  |  |
Senior notes issued to finance acquisition |  | $ 5,300 |  |  |  |  |  |  |  |  |  |  |
Weighted Average Number of Shares Outstanding, Basic | shares |  | 228,000,000 |  |  |  |  |  |  |  |  |  |  |
Shares Conversion Ratio in Acquisition |  | 0.6019 |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares |  | 137,000,000 |  |  |  |  |  |  |  |  |  |  |
Share Price | $ / shares |  | $ 111.02 |  |  |  |  |  |  |  |  |  |  |
Equity Issued in Business Combination, Fair Value Disclosure |  | $ 15,204 |  |  |  |  |  |  |  |  |  |  |
Business Acquisition, Share Price | $ / shares |  | $ 62.93 |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Businesses, Gross |  | $ 14,319 |  |  |  |  |  |  |  |  |  |  |
Attributed Value Equity Awards Assumed in Acquisition | [7] | 323 |  |  |  |  |  |  |  |  |  |  |
Business Combination, Consideration Transferred |  | 29,846 |  |  |  |  |  |  |  |  |  |  |
Cash |  | 71 |  |  |  |  |  |  |  |  |  |  |
Investments |  | 42,967 |  |  |  |  |  |  |  |  |  |  |
Accrued investment income |  | 359 |  |  |  |  |  |  |  |  |  |  |
Insurance and reinsurance balances receivable |  | 3,095 |  |  |  |  |  |  |  |  |  |  |
Reinsurance recoverable on paid losses and loss expenses |  | 1,676 |  |  |  |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets |  | 2,860 |  |  |  |  |  |  |  |  |  |  |
Finite lived intangible assets |  | 4,795 |  |  |  |  |  |  |  |  |  |  |
Prepaid reinsurance premiums |  | 280 |  |  |  |  |  |  |  |  |  |  |
Other assets |  | 853 |  |  |  |  |  |  |  |  |  |  |
Unpaid losses and loss expenses |  | (22,923) |  |  |  |  |  |  |  |  |  |  |
Unearned premiums |  | (7,011) |  |  |  |  |  |  |  |  |  |  |
Reinsurance Payable |  | (603) |  |  |  |  |  |  |  |  |  |  |
Accounts Payable, Accrued Expenses and Other Liabilities |  | (2,030) |  |  |  |  |  |  |  |  |  |  |
Deferred Tax Liabilities, Net |  | (1,292) |  |  |  |  |  |  |  |  |  |  |
Long-term Debt |  | (3,765) |  |  |  |  |  |  |  |  |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net |  | 19,332 |  |  |  |  |  |  |  |  |  |  |
Goodwill |  | 10,514 |  |  |  |  |  |  |  |  |  |  |
Goodwill, Expected Tax Deductible Amount |  | $ 0 |  |  |  |  |  |  |  |  |  |  |
Chubb Corp, Revenue since acquisition date |  |  |  |  |  |  | 12,376 |  |  |  |  |  |
Chubb Corp, Earnings since acquisition date |  |  |  |  |  |  | $ 1,756 |  |  |  |  |  |
Chubb Corp, Pro Forma Revenue |  |  |  |  | 31,937 |  |  |  | 32,622 |  |  |  |
Chubb Corp, Pro Forma Net Income (Loss) |  |  |  |  | $ 4,183 |  |  |  | $ 4,478 |  |  |  |
Chubb Corp, Pro Forma Earnings Per Share, Basic | $ / shares |  |  |  |  | $ 8.95 |  |  |  | $ 9.61 |  |  |  |
Chubb Corp, Pro Forma Earnings Per Share, Diluted | $ / shares |  |  |  |  | $ 8.88 |  |  |  | $ 9.52 |  |  |  |
[1] | Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2017 and 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2] | Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[3] | Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2016 and 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[4] | Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[5] | Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2015 and 2014, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[6] | (1) Net of a provision for uncollectible reinsurance.
[7] | (1) The fair value of the replacement equity awards was $525 million, of which $323 million was attributed to service periods prior to the acquisition and was included in the purchase consideration. Refer to Note 12 for further information on these replacement equity awards.

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- Definition Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e31931-109318 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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- Definition Fair value of equity issued in a business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 + Details
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- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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- Definition Sum of the carrying amounts as of the balance sheet date of all investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(h)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of assets classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(10)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(10)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(17)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585 + Details
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- Definition The carrying amount as of the balance sheet date due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, net of the allowance for doubtful accounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.(a),5) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition The unexpired portion of premiums ceded on policies in force as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6485982&loc=d3e22818-158507 + Details
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- Definition Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21412-158489 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21409-158489 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387 + Details
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- Definition Value, after forfeitures, of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 30 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=95456744&loc=d3e3913-113898 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 30 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6418191&loc=d3e15009-113911 + Details
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- Definition Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(13)(a)(2)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-16(Column D)) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915 + Details
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- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1448-109256 + Details
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