Income Taxes - Schedule of Changes in Valuation Allowance (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Income Tax Disclosure [Abstract] | |||
| Balance at beginning of year | $ 1,668 | $ 1,804 | $ 1,400 |
| Increase to allowance | 472 | 117 | 471 |
| Release of allowance | (42) | (77) | (41) |
| Acquisitions and divestitures (F) | 29 | (37) | |
| U.S. state tax apportionment and tax rate changes | (45) | (80) | (32) |
| Foreign currency translation | (45) | (59) | 6 |
| Balance at end of year | $ 2,037 | $ 1,668 | $ 1,804 |