Pension Benefits Narrative (Details) - USD ($) $ in Millions |
9 Months Ended | 12 Months Ended | |
|---|---|---|---|
Sep. 30, 2016 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Defined Benefit Plan Disclosure [Line Items] | |||
| Defined Benefit Pension Plan, Postemployment Benefit Period | 5 years | ||
| Other Postretirement Benefits Payable | $ 3 | $ 3 | |
| Change in Accounting Method Accounted for as Change in Estimate | Scenario, Forecast | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Expected impact of change in estimation of pension net periodic benefit cost | $ 10 |