Pension plans - Additional tabular disclosures (Detail) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate applicable to pension benefit obligations | 3.90% | 3.30% | 3.80% |
| Expected long-term rate of return on plan assets | 6.40% | 6.40% | 6.10% |
| Rate of compensation increase | 2.60% | 2.80% | 3.00% |
| Discount rate applicable to net periodic pension expense | 3.40% | 3.90% | 4.20% |
| Amounts recognized in other comprehensive income: | |||
| Accumulated other comprehensive income (loss), beginning of year | $ (614) | $ (839) | |
| Amount included in net periodic pension expense | 116 | 155 | |
| Actuarial gains (losses) and other | (686) | 70 | |
| Accumulated other comprehensive income (loss), end of year | $ (1,184) | $ (614) | $ (839) |