Retirement Benefits (Unaudited) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Components of Net Periodic Benefit Cost
Defined contribution plan, employer contributions	$ 100	$ 88	$ 356	$ 279
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	102	92	204	184
Interest cost	306	340	613	680
Expected return on plan assets	(594)	(526)	(1,188)	(1,051)
Amortization of prior service credit	(15)	(14)	(30)	(29)
Net periodic benefit cost (benefit)	(201)	(108)	(401)	(216)
Defined benefit plan, contributions by Employer	26	23	46	46
OPB
Components of Net Periodic Benefit Cost
Service cost	5	4	9	8
Interest cost	16	20	33	40
Expected return on plan assets	(25)	(23)	(51)	(46)
Amortization of prior service credit	1	0	2	(1)
Net periodic benefit cost (benefit)	(3)	1	(7)	1
Defined benefit plan, contributions by Employer	$ 11	$ 12	$ 23	$ 24