Pension Benefits Narrative (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Compensation and Retirement Disclosure [Abstract] | |||
| Defined Benefit Pension Plan, Postemployment Benefit Period | 5 years | ||
| Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year | $ 89 | ||
| Defined Contribution Plan, Cost Recognized | $ 51 | $ 55 | $ 49 |