Pension Plans and Postretirement Benefits (Benefit Obligation and Expense for Our Split-Dollar Life Insurance Agreements) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Postretirement and Pension Plans | |||
| Benefit obligation | $ 233 | $ 217 | $ 212 |
| Other operating and administrative expenses | $ 67 | $ 52 | $ 50 |