Summary of Reconciliation of Segment Operating Revenues (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2016 |
Mar. 31, 2015 |
|
| Segment Reporting, Revenue Reconciling Item [Line Items] | ||
| Segment reporting information, revenue | $ 32,171 | $ 31,984 |
| Operating Segments | ||
| Segment Reporting, Revenue Reconciling Item [Line Items] | ||
| Segment reporting information, revenue | 31,294 | 31,797 |
| Corporate and Other | ||
| Segment Reporting, Revenue Reconciling Item [Line Items] | ||
| Segment reporting information, revenue | 1,232 | 474 |
| Eliminations | ||
| Segment Reporting, Revenue Reconciling Item [Line Items] | ||
| Segment reporting information, revenue | $ (355) | $ (287) |