Retirement Benefits (Details 10) $ in Millions	Dec. 31, 2017 USD ($)
Estimated Benefit Payments (Table Amounts) [Abstract]
2018	$ 1,722
2019	1,771
2020	1,809
2021	1,857
2022	1,900
2023 through 2027	10,086
Pension Benefits
Estimated Benefit Payments (Table Amounts) [Abstract]
2018	1,573
2019	1,618
2020	1,665
2021	1,713
2022	1,757
2023 through 2027	9,410
Medical and Life Benefits
Estimated Benefit Payments (Table Amounts) [Abstract]
2018	149
2019	153
2020	144
2021	144
2022	143
2023 through 2027	$ 676