|
Summary of Reconciliation of Segment Operating Revenues (Detail) (USD $)
In Millions, unless otherwise specified |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
Dec. 31, 2014
|
Sep. 30, 2014
|
Jun. 30, 2014
|
Mar. 31, 2014
|
Dec. 31, 2013
|
Sep. 30, 2013
|
Jun. 30, 2013
|
Mar. 31, 2013
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
|
| Segment Reporting, Revenue Reconciling Item [Line Items] | |||||||||||
| Operating Revenues | $ 33,192 | $ 31,586 | $ 31,483 | $ 30,818 | $ 31,065 | $ 30,279 | $ 29,786 | $ 29,420 | $ 127,079 | $ 120,550 | $ 115,846 |
| Operating Segments | |||||||||||
| Segment Reporting, Revenue Reconciling Item [Line Items] | |||||||||||
| Operating Revenues | 126,075 | 119,647 | 114,813 | ||||||||
| Revenue Generated By Assets Sold | |||||||||||
| Segment Reporting, Revenue Reconciling Item [Line Items] | |||||||||||
| Operating Revenues | 256 | 599 | 835 | ||||||||
| Corporate, Eliminations and Other | |||||||||||
| Segment Reporting, Revenue Reconciling Item [Line Items] | |||||||||||
| Operating Revenues | $ 748 | $ 304 | $ 198 | ||||||||