Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension settlement costs				$ 34
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 21	$ 22	$ 63	70
Interest cost on projected benefit obligation	33	31	98	91
Expected return on plan assets	(43)	(45)	(129)	(143)
Amortization of unrecognized (gain) loss	14	4	42	17
Net periodic pension benefit cost	25	12	74	35
Pension settlement costs		9		34
Net periodic benefit cost	25	21	74	69
Postretirement Benefits Other Than Pensions (OPEB) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	4	5	14	16
Interest cost on projected benefit obligation	10	9	31	28
Amortization of prior service cost (credit)	(3)	(1)	(7)	(6)
Amortization of unrecognized (gain) loss	1		(1)	1
Net periodic benefit cost	$ 12	$ 13	$ 37	$ 39