Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension settlement costs			$ 159
Total pension benefit cost	$ 39	$ 25	213	$ 74
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	24	21	73	63
Interest cost on projected benefit obligation	26	33	84	98
Expected return on plan assets	(40)	(43)	(129)	(129)
Amortization of unrecognized (gain) loss	29	14	76	42
Net periodic benefit cost	39	25	104	74
Pension settlement costs			159
Gain on disposal, net			(50)
Postretirement Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5	4	15	14
Interest cost on projected benefit obligation	8	10	24	31
Amortization of prior service cost (credit)	(8)	(3)	(24)	(7)
Amortization of unrecognized (gain) loss	1	1	4	(1)
Gain on disposal, net			(24)
Total pension benefit cost	6	12	19	37
Total periodic postretirement benefit cost	$ 6	$ 12	$ (5)	$ 37