Income Taxes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |
|---|---|---|---|
Jun. 30, 2017 |
Jun. 30, 2016 |
Jun. 30, 2017 |
|
| Income Tax Disclosure [Abstract] | |||
| Excess tax benefits recognized | $ 8 | $ 26 | |
| Tax benefit from foreign Supreme Court decision | $ 13 | ||
| Tax benefit from prior year tax positions currently being challenged | $ 15 | $ 15 | |