Derivative contracts - Narrative (Detail) - USD ($)
|
12 Months Ended |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
| Derivative [Line Items] |
|
|
|
| Derivative contract gains (losses) |
$ (300,000,000)
|
$ 718,000,000
|
$ 751,000,000
|
| Not Designated as Hedging Instrument [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Derivative contract gains (losses) |
|
|
751,000,000
|
| Collateral posting requirements under contracts with collateral provisions |
0
|
|
|
| Additional collateral posting requirements |
1,100,000,000
|
|
|
| Not Designated as Hedging Instrument [Member] | Equity Index Put Options [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Derivative contract gains (losses) |
$ (300,000,000)
|
718,000,000
|
662,000,000
|
| Weighted average remaining life of derivative contracts |
1 year 10 months 24 days
|
|
|
| Notional value of contracts expired and terminated |
$ 1,200,000,000
|
|
|
| Notional value of contracts that will expire in next fiscal year |
12,200,000,000
|
|
|
| Premiums received at contract inception dates |
4,000,000,000
|
|
|
| Aggregate intrinsic value of equity index put option contracts |
1,653,000,000
|
789,000,000
|
|
| Liabilities |
$ 2,452,000,000
|
2,172,000,000
|
|
| Not Designated as Hedging Instrument [Member] | Equity Index Put Options [Member] | Maximum [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Derivative inception month and year |
2008-03
|
|
|
| Derivative maturity month and year |
2025-10
|
|
|
| Not Designated as Hedging Instrument [Member] | Equity Index Put Options [Member] | Minimum [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Derivative maturity month and year |
2019-04
|
|
|
| Not Designated as Hedging Instrument [Member] | Credit Default [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Derivative contract gains (losses) |
|
|
$ 89,000,000
|
| Other Assets [Member] | Not Designated as Hedging Instrument [Member] | Utilities and Energy [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Assets |
$ 172,000,000
|
142,000,000
|
|
| Accounts Payable, Accruals and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] | Utilities and Energy [Member] |
|
|
|
| Derivative [Line Items] |
|
|
|
| Liabilities |
$ 111,000,000
|
$ 82,000,000
|
|