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Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Condensed Statement of Income Captions [Line Items] |  |  |  |
Net premiums written | $ 9,078 | $ 8,622 | $ 25,410 | $ 24,278
Net premiums earned | 8,765 | 8,327 | 24,687 | 23,355
Net investment income | 840 | 873 | 2,528 | 2,568
Equity In Earnings Of Subsidiaries | 0 | 0 | 0 | 0
Net Realized Gains Losses | (141) | (155) | (1,069) | (475)
Net gains (losses) recognized during the period | (141) | (155) | (1,069) | (475)
Losses and loss expenses | 5,835 | 5,052 | 16,897 | 13,865
Policy benefits | 198 | 158 | 550 | 515
Policy acquisition costs and administrative expenses | 2,378 | 2,355 | 7,054 | 6,831
Interest (income) expense | 130 | 138 | 390 | 418
Other (income) expense | (485) | (57) | (372) | (326)
Amortization of purchased intangibles | 72 | 76 | 217 | 229
Chubb integration expenses | 0 | 2 | 0 | 9
Income tax expense | 142 | 230 | 295 | 626
Net income | 1,194 | 1,091 | 1,115 | 3,281
Comprehensive income (loss) | 1,952 | 1,473 | 2,352 | 6,250
Chubb Limited (Parent Guarantor) |  |  |  |
Condensed Statement of Income Captions [Line Items] |  |  |  |
Net premiums written | 0 | 0 | 0 | 0
Net premiums earned | 0 | 0 | 0 | 0
Net investment income | 0 | 1 | (2) | 3
Equity In Earnings Of Subsidiaries | 1,174 | 1,053 | 1,064 | 3,147
Net gains (losses) recognized during the period | 3 | (4) | 5 | 1
Losses and loss expenses | 0 | 0 | 0 | 0
Policy benefits | 0 | 0 | 0 | 0
Policy acquisition costs and administrative expenses | 21 | 22 | 66 | 64
Interest (income) expense | (34) | (59) | (103) | (187)
Other (income) expense | (10) | (7) | (27) | (19)
Amortization of purchased intangibles | 0 | 0 | 0 | 0
Chubb integration expenses |  | 0 |  | 0
Income tax expense | 6 | 3 | 16 | 12
Net income | 1,194 | 1,091 | 1,115 | 3,281
Comprehensive income (loss) | 1,952 | 1,473 | 2,352 | 6,250
Chubb INA Holdings Inc (Subsidiary Issuer) |  |  |  |
Condensed Statement of Income Captions [Line Items] |  |  |  |
Net premiums written | 0 | 0 | 0 | 0
Net premiums earned | 0 | 0 | 0 | 0
Net investment income | 1 | (3) | 6 | (13)
Equity In Earnings Of Subsidiaries | 516 | 824 | 838 | 2,345
Net gains (losses) recognized during the period | (192) | 68 | (271) | 34
Losses and loss expenses | 0 | 0 | 0 | 0
Policy benefits | 0 | 0 | 0 | 0
Policy acquisition costs and administrative expenses | (33) | (5) | (101) | (25)
Interest (income) expense | 151 | 171 | 448 | 536
Other (income) expense | (2) | (3) | 1 | 1
Amortization of purchased intangibles | 0 | 0 | 0 | 0
Chubb integration expenses |  | 0 |  | 2
Income tax expense | (66) | (33) | (125) | (120)
Net income | 275 | 759 | 350 | 1,972
Comprehensive income (loss) | 812 | 1,138 | 1,484 | 4,476
Other Chubb Limited Subsidiaries |  |  |  |
Condensed Statement of Income Captions [Line Items] |  |  |  |
Net premiums written | 9,078 | 8,622 | 25,410 | 24,278
Net premiums earned | 8,765 | 8,327 | 24,687 | 23,355
Net investment income | 839 | 875 | 2,524 | 2,578
Equity In Earnings Of Subsidiaries | 0 | 0 | 0 | 0
Net gains (losses) recognized during the period | 48 | (219) | (803) | (510)
Losses and loss expenses | 5,835 | 5,052 | 16,897 | 13,865
Policy benefits | 198 | 158 | 550 | 515
Policy acquisition costs and administrative expenses | 2,390 | 2,338 | 7,089 | 6,792
Interest (income) expense | 13 | 26 | 45 | 69
Other (income) expense | (473) | (47) | (346) | (308)
Amortization of purchased intangibles | 72 | 76 | 217 | 229
Chubb integration expenses |  | 2 |  | 7
Income tax expense | 202 | 260 | 404 | 734
Net income | 1,415 | 1,118 | 1,552 | 3,520
Comprehensive income (loss) | 2,180 | 1,517 | 2,840 | 6,486
Consolidating Adjustments and Eliminations |  |  |  |
Condensed Statement of Income Captions [Line Items] |  |  |  |
Net premiums written | 0 | 0 | 0 | 0
Net premiums earned | 0 | 0 | 0 | 0
Net investment income | 0 | 0 | 0 | 0
Equity In Earnings Of Subsidiaries | (1,690) | (1,877) | (1,902) | (5,492)
Net gains (losses) recognized during the period | 0 | 0 | 0 | 0
Losses and loss expenses | 0 | 0 | 0 | 0
Policy benefits | 0 | 0 | 0 | 0
Policy acquisition costs and administrative expenses | 0 | 0 | 0 | 0
Interest (income) expense | 0 | 0 | 0 | 0
Other (income) expense | 0 | 0 | 0 | 0
Amortization of purchased intangibles | 0 | 0 | 0 | 0
Chubb integration expenses |  | 0 |  | 0
Income tax expense | 0 | 0 | 0 | 0
Net income | (1,690) | (1,877) | (1,902) | (5,492)
Comprehensive income (loss) | $ (2,992) | $ (2,655) | $ (4,324) | $ (10,962)

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