v3.2.0.727
Segment Information (Operations By Segment) (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Segment Reporting Information [Line Items]        
Net premiums written $ 4,784 $ 4,559 $ 8,860 $ 8,744
Net premiums earned 4,360 4,332 8,287 8,302
Losses and loss expenses 2,417 2,388 4,539 4,549
Policy benefits 153 144 295 258
Policy acquisition costs 727 758 1,434 1,486
Administrative expenses 578 566 1,132 1,101
Underwriting income (loss) 485 476 887 908
Net investment income 562 556 1,113 1,109
Net realized gains (losses) including OTTI 126 (73) 37 (177)
Interest expense 71 72 139 143
(Gains) losses from fair value changes in separate account assets (6) (17) (17) (11)
Other 23 (8) 29 (31)
Other (income) expense 17 (25) 12 (42)
Income tax expense (benefit) 143 133 263 226
Net income (loss) 942 779 1,623 1,513
Insurance - North American P&C [Member]        
Segment Reporting Information [Line Items]        
Net premiums written 1,975 1,635 3,405 3,053
Net premiums earned 1,688 1,542 3,214 3,029
Losses and loss expenses 1,120 1,016 2,155 1,956
Policy acquisition costs 130 152 291 311
Administrative expenses 189 175 360 336
Underwriting income (loss) 249 199 408 426
Net investment income 269 265 532 535
Net realized gains (losses) including OTTI 0 (11) (6) (20)
Interest expense 2 2 4 5
Other 23 (24) 16 (44)
Income tax expense (benefit) 89 91 169 174
Net income (loss) 404 384 745 806
Insurance - North American Agriculture [Member]        
Segment Reporting Information [Line Items]        
Underwriting Income Including Losses Related to Crop Derivatives 21      
Net premiums written 379 388 467 582
Net premiums earned 321 330 385 433
Losses and loss expenses 271 287 293 413
Policy acquisition costs 23 23 19 28
Administrative expenses 4 1 3 2
Underwriting income (loss) 23 19 70 (10)
Net investment income 6 6 12 13
Net realized gains (losses) including OTTI (2) 8 (2) 6
Interest expense 0 0 0 0
Other 8 9 16 17
Income tax expense (benefit) 4 5 14 (2)
Net income (loss) 15 19 50 (6)
Crop Derivative Gain or Loss 2      
Insurance - Overseas General [Member]        
Segment Reporting Information [Line Items]        
Net premiums written 1,669 1,760 3,463 3,531
Net premiums earned 1,644 1,709 3,281 3,321
Losses and loss expenses 816 830 1,630 1,647
Policy acquisition costs 396 402 785 788
Administrative expenses 254 256 510 506
Underwriting income (loss) 178 221 356 380
Net investment income 139 136 277 268
Net realized gains (losses) including OTTI 13 14 3 4
Interest expense 1 1 2 2
Other 8 8 25 2
Income tax expense (benefit) 69 55 121 92
Net income (loss) 252 307 488 556
Global Reinsurance [Member]        
Segment Reporting Information [Line Items]        
Net premiums written 261 278 534 586
Net premiums earned 220 261 446 545
Losses and loss expenses 72 109 171 235
Policy acquisition costs 60 60 114 127
Administrative expenses 13 14 25 28
Underwriting income (loss) 75 78 136 155
Net investment income 79 80 154 157
Net realized gains (losses) including OTTI 5 (15) (6) (23)
Interest expense 1 2 2 3
Other (3) (10) (8) (29)
Income tax expense (benefit) 7 10 15 20
Net income (loss) 154 141 275 295
Life [Member]        
Segment Reporting Information [Line Items]        
Life underwriting income 77      
Net premiums written 500 498 991 992
Net premiums earned 487 490 961 974
Losses and loss expenses 137 146 289 297
Policy benefits 153 144 295 258
Policy acquisition costs 118 121 225 232
Administrative expenses 74 73 147 141
Underwriting income (loss) 5 6 5 46
Net investment income 66 66 132 130
Net realized gains (losses) including OTTI 103 (72) 44 (148)
Interest expense 2 3 3 6
(Gains) losses from fair value changes in separate account assets (6) (17) (17) (11)
Other (17) 4 (29) 11
Income tax expense (benefit) 10 12 19 22
Net income (loss) 185 (2) 205 0
Corporate And Other [Member]        
Segment Reporting Information [Line Items]        
Losses and loss expenses 1 0 1 1
Policy acquisition costs   0   0
Administrative expenses 44 47 87 88
Underwriting income (loss) (45) (47) (88) (89)
Net investment income 3 3 6 6
Net realized gains (losses) including OTTI 7 3 4 4
Interest expense 65 64 128 127
Other 4 5 9 12
Income tax expense (benefit) (36) (40) (75) (80)
Net income (loss) $ (68) $ (70) $ (140) $ (138)