Intangible Assets - Carrying Amounts of Identifiable Intangible Assets (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
Jun. 30, 2016 |
|
| Schedule Of Intangible Assets [Line Items] | ||||
| Indefinite-lived intangible assets, Beginning balance | $ 17,178 | |||
| Indefinite-lived intangible assets, Ending balance | $ 17,178 | 17,178 | ||
| Finite-lived intangible assets, Beginning balance | 185 | |||
| Finite-lived intangible assets, amortization expense | (25) | $ (25) | (50) | $ (50) |
| Finite-lived intangible assets, Ending balance | 245 | 245 | ||
| Intangible assets, Beginning balance | 17,363 | |||
| Intangible assets, Ending balance | $ 17,423 | 17,423 | ||
| First Reserve Transaction [Member] | ||||
| Schedule Of Intangible Assets [Line Items] | ||||
| Finite-lived intangible assets, acquisition | 110 | |||
| Intangible assets, acquisition | $ 110 | |||