Retirement Benefits Plans Retirement Benefits Plans - Defined Contribution Plans (Details 13) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract] | |||
| Employer contributions to defined contribution plans | $ 137 | $ 141 | $ 121 |