Retirement Benefits Net Periodic Benefit Cost (Benefit) (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Mark-to-market expense (benefit)	$ (1,034)	$ (1,800)	$ (655)
Pension Benefits
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Service cost	409	367	404
Interest cost	1,226	1,360	1,226
Expected return on plan assets	(2,376)	(2,101)	(2,217)
Amortization of prior service cost (credit)	(59)	(59)	(58)
Mark-to-market expense (benefit)	(1,034)	(1,783)	(699)
Other	10	0	0
Net periodic benefit cost (benefit)	244	1,350	54
Medical and Life Benefits
Components of Net Periodic Benefit Cost (Table Amounts) [Abstract]
Service cost	17	16	21
Interest cost	67	80	76
Expected return on plan assets	(102)	(92)	(101)
Amortization of prior service cost (credit)	4	(3)	(21)
Mark-to-market expense (benefit)	0	(17)	44
Other	2	0	0
Net periodic benefit cost (benefit)	$ (12)	$ 18	$ (69)