Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension settlement costs			$ 159
Net periodic benefit cost	$ 49	$ 24	174	$ 49
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	24	21	49	42
Interest cost on projected benefit obligation	28	32	58	65
Expected return on plan assets	(39)	(43)	(89)	(86)
Amortization of unrecognized (gain) loss	30	14	47	28
Net periodic pension benefit cost	43	24	65	49
Pension settlement costs	56		159
One-time gain on disposal, net	(50)		(50)
Postretirement Costs [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5	5	10	10
Interest cost on projected benefit obligation	8	11	16	21
Amortization of prior service cost (credit)	(8)	(3)	(16)	(4)
Amortization of unrecognized (gain) loss	1		3	(2)
One-time gain on disposal, net	(24)		(24)
Net periodic benefit cost	6	13	13	25
Total periodic postretirement benefit cost	$ (18)	$ 13	$ (11)	$ 25