Retroactive reinsurance contracts - Reconciliation of changes in claim liabilities and deferred charge assets (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] |
|
|
|
| Unpaid losses and loss adjustment expenses, beginning of year |
$ 42,937
|
$ 24,972
|
$ 24,058
|
| Unpaid losses and loss adjustment expenses, end of year |
41,834
|
42,937
|
24,972
|
| Deferred charges reinsurance assumed, beginning of year |
(15,278)
|
(8,047)
|
(7,687)
|
| Deferred charges reinsurance assumed, end of year |
(14,104)
|
(15,278)
|
(8,047)
|
| Retroactive Reinsurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses, prior years' contracts |
919
|
458
|
451
|
| Total incurred losses and loss adjustment expenses |
1,436
|
11,733
|
1,713
|
| Unpaid Losses and Loss Adjustment Expenses [Member] | Retroactive Reinsurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses, current year contracts |
603
|
19,005
|
2,136
|
| Incurred losses and loss adjustment expenses, prior years' contracts |
(341)
|
(41)
|
(63)
|
| Total incurred losses and loss adjustment expenses |
262
|
18,964
|
2,073
|
| Paid losses and loss adjustment expenses |
(1,365)
|
(999)
|
(1,159)
|
| Deferred Charges Reinsurance Assumed [Member] | Retroactive Reinsurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses, current year contracts |
(86)
|
(7,730)
|
(874)
|
| Incurred losses and loss adjustment expenses, prior years' contracts |
1,260
|
499
|
514
|
| Total incurred losses and loss adjustment expenses |
$ 1,174
|
$ (7,231)
|
$ (360)
|