Unpaid losses and loss adjustment expenses - Narrative (Detail)
$ in Millions |
12 Months Ended |
|
Dec. 31, 2018
USD ($)
Event
|
Dec. 31, 2017
USD ($)
Event
|
Dec. 31, 2016
USD ($)
|
| 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 with respect to current accident year events |
$ 39,876
|
$ 37,702
|
$ 30,636
|
| Number of significant catastrophe events | Event |
4
|
6
|
|
| Incurred losses and loss adjustment expenses for (reductions of) prior years' accident events |
$ (1,406)
|
$ (544)
|
$ (1,443)
|
| Percentage of reduction of net liabilities |
2.40%
|
1.10%
|
3.10%
|
| Liabilities for environmental, asbestos and latent injury claims, net of reinsurance |
$ 1,700
|
$ 1,600
|
|
| Property and Casualty Insurance and Reinsurance, Excluding Retroactive Reinsurance [Member] | Significant Catastrophe Events [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses with respect to current accident year events |
1,600
|
3,000
|
|
| Primary Insurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses for (reductions of) prior years' accident events |
(937)
|
(249)
|
$ (569)
|
| Property and Casualty Reinsurance [Member] |
|
|
|
| Liability for Claims and Claims Adjustment Expense [Line Items] |
|
|
|
| Incurred losses and loss adjustment expenses for (reductions of) prior years' accident events |
$ (469)
|
$ (295)
|
$ (874)
|