Retirement Programs - Pension and Postretirement Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Settlement charges					$ 0
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost			$ (4)	$ (4)	9
Pensions
Defined Benefit Plan Disclosure [Line Items]
Service cost			74	46	45
Interest cost			128	103	100
Expected return on plan assets			(219)	(161)	(157)
Net amortization and deferral			71	68	59
Curtailment gain			0	0	0
Settlement charges	$ (10)	$ (4)	14	2	4
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost			(6)	12	6
Settlement gains from divestitures			(44)	0	0
Net periodic benefit cost (benefit)			24	58	51
OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost			2	3	2
Interest cost			5	5	6
Expected return on plan assets			0
Net amortization and deferral			(3)	(3)	(3)
Curtailment gain			0	(18)	0
Settlement charges			0
Amount recognized in Net pension and OPEB cost (benefit), excluding service cost			2	(16)	3
Settlement gains from divestitures			0	0	0
Net periodic benefit cost (benefit)			$ 4	$ (13)	$ 5