Retirement Benefits (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	$ 912	$ 501	$ 4,067
Change in prior service cost	0		(92)
Amortization of:
Prior service credit	82	88	104
Net loss from previous years	(730)	(709)	(340)
Tax expense (benefit) related to above items	(89)	45	(1,423)
Change in unamortized benefit plan costs	175	(75)	2,316
Pension Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	1,003	626	3,833
Change in prior service cost	0		0
Amortization of:
Prior service credit	60	60	59
Net loss from previous years	(714)	(682)	(327)
Tax expense (benefit) related to above items	(121)	(1)	(1,357)
Change in unamortized benefit plan costs	228	3	2,208
Medical and Life Benefits
Changes in Unamortized Benefit plan Costs (Table Amounts) [Abstract]
Change in net actuarial loss	(91)	(125)	234
Change in prior service cost	0		(92)
Amortization of:
Prior service credit	22	28	45
Net loss from previous years	(16)	(27)	(13)
Tax expense (benefit) related to above items	32	46	(66)
Change in unamortized benefit plan costs	$ (53)	$ (78)	$ 108