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Segment Information (Operations By Segment) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Segment Reporting Information [Line Items] |  |  |
Net premiums written | $ 37,868 | $ 33,820 | $ 32,275
Net premiums earned | 36,355 | 33,117 | 31,290
Losses and loss expenses | 21,980 | 21,710 | 18,730
Policy benefits | 699 | 784 | 740
Policy acquisition costs | 6,918 | 6,547 | 6,153
Administrative expenses | 3,136 | 2,979 | 3,030
Underwriting income (loss) | 3,622 | 1,097 | 2,637
Net investment income (loss) | 3,456 | 3,375 | 3,426
Other (income) expense | (2,365) | (994) | (596)
Amortization of purchased intangibles | 287 | 290 | 305
Segment income | 9,156 | 5,176 | 6,354
Net realized gains (losses) (includes $3, $(281), and $(31) reclassified from AOCI) | 1,152 | (498) | (530)
Interest expense | 492 | 516 | 552
Income tax expense | 1,277 | 629 | 795
Chubb integration expenses | 0 | 0 | 23
Net income | 8,539 | 3,533 | 4,454
Segment Reconciling Items [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 0 | 0 | 0
Net premiums earned | 0 | 0 | 0
Losses and loss expenses | (8) | 1 | (8)
Policy benefits | (8) | 58 | 44
Policy acquisition costs | 0 | 0 | 0
Administrative expenses | 0 | 0 | 0
Underwriting income (loss) | 16 | (59) | (36)
Net investment income (loss) | (179) | (115) | (86)
Other (income) expense | (171) | (173) | (130)
Amortization of purchased intangibles | 0 | 0 | 0
Segment income | 8 | (1) | 8
Net realized gains (losses) (includes $3, $(281), and $(31) reclassified from AOCI) | (8) | 1 | (8)
Interest expense | 0 | 0 | 0
Income tax expense | 0 | 0 | 0
Chubb integration expenses |  |  | 0
Net income | 0 | 0 | 0
North America Commercial P&C Insurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 16,415 | 14,474 | 13,375
Net premiums earned | 15,461 | 13,964 | 12,922
Losses and loss expenses | 10,015 | 10,129 | 8,206
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 2,082 | 1,942 | 1,831
Administrative expenses | 1,052 | 1,006 | 1,028
Underwriting income (loss) | 2,312 | 887 | 1,857
Net investment income (loss) | 2,078 | 2,061 | 2,109
Other (income) expense | 31 | 23 | 24
Amortization of purchased intangibles | 0 | 0 | 0
Segment income | 4,359 | 2,925 | 3,942
North America Personal P&C Insurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 5,002 | 4,920 | 4,787
Net premiums earned | 4,915 | 4,866 | 4,694
Losses and loss expenses | 2,924 | 3,187 | 3,043
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 1,001 | 974 | 948
Administrative expenses | 276 | 270 | 286
Underwriting income (loss) | 714 | 435 | 417
Net investment income (loss) | 249 | 260 | 258
Other (income) expense | (2) | 5 | 3
Amortization of purchased intangibles | 10 | 11 | 12
Segment income | 955 | 679 | 660
North America Agricultural Insurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 2,388 | 1,846 | 1,810
Net premiums earned | 2,338 | 1,822 | 1,795
Losses and loss expenses | 1,962 | 1,544 | 1,616
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 124 | 123 | 84
Administrative expenses | (3) | 9 | 6
Underwriting income (loss) | 255 | 146 | 89
Net investment income (loss) | 28 | 30 | 30
Other (income) expense | 1 | 1 | 1
Amortization of purchased intangibles | 26 | 27 | 28
Segment income | 256 | 148 | 90
Overseas General Insurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 10,713 | 9,335 | 9,262
Net premiums earned | 10,441 | 9,285 | 8,882
Losses and loss expenses | 5,143 | 5,255 | 4,606
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 2,799 | 2,568 | 2,501
Administrative expenses | 1,078 | 1,034 | 1,033
Underwriting income (loss) | 1,421 | 428 | 742
Net investment income (loss) | 597 | 534 | 588
Other (income) expense | 0 | 13 | 12
Amortization of purchased intangibles | 48 | 45 | 45
Segment income | 1,970 | 904 | 1,273
Global Reinsurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 873 | 731 | 649
Net premiums earned | 798 | 698 | 654
Losses and loss expenses | 632 | 435 | 352
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 200 | 174 | 169
Administrative expenses | 35 | 37 | 35
Underwriting income (loss) | (69) | 52 | 98
Net investment income (loss) | 331 | 307 | 279
Other (income) expense | 0 | 2 | 1
Amortization of purchased intangibles | 0 | 0 | 0
Segment income | 262 | 357 | 376
Life Insurance [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 2,477 | 2,514 | 2,392
Net premiums earned | 2,402 | 2,482 | 2,343
Losses and loss expenses | 740 | 724 | 757
Policy benefits | 707 | 726 | 696
Policy acquisition costs | 712 | 766 | 620
Administrative expenses | 333 | 320 | 323
Underwriting income (loss) | (90) | (54) | (53)
Net investment income (loss) | 407 | 385 | 373
Other (income) expense | (106) | (74) | (48)
Amortization of purchased intangibles | 5 | 4 | 2
Segment income | 418 | 401 | 366
Corporate and Other |  |  |
Segment Reporting Information [Line Items] |  |  |
Net premiums written | 0 | 0 | 0
Net premiums earned | 0 | 0 | 0
Losses and loss expenses | 572 | 435 | 158
Policy benefits | 0 | 0 | 0
Policy acquisition costs | 0 | 0 | 0
Administrative expenses | 365 | 303 | 319
Underwriting income (loss) | (937) | (738) | (477)
Net investment income (loss) | (55) | (87) | (125)
Other (income) expense | (2,118) | (791) | (459)
Amortization of purchased intangibles | 198 | 203 | 218
Segment income | 928 | (237) | (361)
Net realized gains (losses) (includes $3, $(281), and $(31) reclassified from AOCI) | 1,160 | (499) | (522)
Interest expense | 492 | 516 | 552
Income tax expense | 1,277 | 629 | 795
Chubb integration expenses |  |  | 23
Net income | $ 319 | $ (1,881) | $ (2,253)

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