Condensed Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions |
Mar. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Statement of Financial Position [Abstract] | ||
| Receivables, allowance for doubtful accounts | $ 53 | $ 51 |
| Property, accumulated depreciation | $ 4,557 | $ 4,434 |