Retirement Benefits Plans Retirement Benefits Plans - Discount Rates (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Retirement Benefits Plans - Discount Rates [Line Items] | ||
| Discount Rates for Service and Interest Costs | 4.00% | |
| Scenario, Forecast [Member] | ||
| Retirement Benefits Plans - Discount Rates [Line Items] | ||
| Discount Rate Service Costs | 4.30% | |
| Discount Rate Interest Costs | 3.30% | |
| Service Cost Reduction | $ 3 | |
| Interest Cost Reduction | $ 42 | |