Retirement Benefits (Details 3) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amounts recorded in accumulated other comprehensive loss (Table Amounts)
Unamortized benefit plan costs	$ (4,586)	$ (5,416)
Pension Benefits
Amounts recorded in accumulated other comprehensive loss (Table Amounts)
Net actuarial loss	(7,842)	(9,030)
Prior service credit	187	244
Income tax benefits related to above items	3,042	3,407
Unamortized benefit plan costs	(4,613)	(5,379)
Medical and Life Benefits
Amounts recorded in accumulated other comprehensive loss (Table Amounts)
Net actuarial loss	(9)	(113)
Prior service credit	22	44
Income tax benefits related to above items	14	32
Unamortized benefit plan costs	$ 27	$ (37)