Postretirement Plans - Additional Information (Detail) - USD ($) |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 25, 2017 |
Jun. 26, 2016 |
Jun. 25, 2017 |
Jun. 26, 2016 |
|
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Recognition of previously deferred postretirement benefit plan amounts, net of tax | $ 200,000,000 | $ 173,000,000 | $ 402,000,000 | $ 346,000,000 |
| Recognition of previously deferred postretirement benefit plan amounts, before tax | 309,000,000 | 267,000,000 | 621,000,000 | 535,000,000 |
| Other postretirement benefit plans | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Recognition of previously deferred postretirement benefit plan amounts, before tax | 13,000,000 | 5,000,000 | 27,000,000 | 10,000,000 |
| Qualified defined benefit pension plans | ||||
| Defined Benefit Plan Disclosure [Line Items] | ||||
| Contributions made by the employer | $ 0 | $ 0 | $ 0 | $ 0 |