Unpaid losses and loss adjustment expenses - Reconciliation of changes in claim liabilities (Detail) - USD ($)
$ in Millions |
12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Gross liabilities at beginning of year |
$ 61,122
|
$ 53,379
|
$ 50,519
|
| Reinsurance recoverable on unpaid losses at beginning of year |
(3,201)
|
(3,338)
|
(3,307)
|
| Net liabilities at beginning of year |
57,921
|
50,041
|
47,212
|
| Net liabilities at end of year |
65,398
|
57,921
|
50,041
|
| Reinsurance recoverable on unpaid losses at end of year |
3,060
|
3,201
|
3,338
|
| Gross liabilities at end of year |
68,458
|
61,122
|
53,379
|
| Property and Casualty Insurance and Reinsurance, Excluding Retroactive Reinsurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses, current accident year events |
39,876
|
37,702
|
30,636
|
| Incurred losses and loss adjustment expenses, prior accident years' events |
(1,406)
|
(544)
|
(1,443)
|
| Total incurred losses and loss adjustment expenses |
38,470
|
37,158
|
29,193
|
| Paid losses and loss adjustment expenses, current accident year events |
(18,391)
|
(17,425)
|
(14,898)
|
| Paid losses and loss adjustment expenses, prior accident years' events |
(15,452)
|
(12,507)
|
(10,929)
|
| Total payments |
(33,843)
|
(29,932)
|
(25,827)
|
| Foreign currency translation adjustment |
(331)
|
$ 654
|
$ (537)
|
| Business acquisition |
$ 3,181
|
|
|