Business segment data - Insurance premiums by geographic area (Detail) - USD ($)
$ in Millions |
12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Property/Casualty [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
$ 52,614
|
$ 56,498
|
$ 41,240
|
| Property/Casualty [Member] | United States [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
46,146
|
50,604
|
35,878
|
| Property/Casualty [Member] | Asia Pacific [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
3,726
|
3,307
|
3,616
|
| Property/Casualty [Member] | Western Europe [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
2,157
|
1,516
|
1,406
|
| Property/Casualty [Member] | All Other Geographic Areas [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
585
|
1,071
|
340
|
| Life/Health [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
6,602
|
5,744
|
5,670
|
| Life/Health [Member] | United States [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
3,598
|
3,320
|
3,473
|
| Life/Health [Member] | Asia Pacific [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
1,361
|
879
|
715
|
| Life/Health [Member] | Western Europe [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
939
|
909
|
822
|
| Life/Health [Member] | All Other Geographic Areas [Member] |
|
|
|
| Segment Reporting Information [Line Items] |
|
|
|
| Premiums written |
$ 704
|
$ 636
|
$ 660
|