Benefit Plans (Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in plan assets:
Balance beginning of period	$ 2,261
Balance end of period	2,025	$ 2,261
Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance at beginning of period	2,749	2,729
Service cost	0	0	$ 0
Interest cost	93	103	113
Participants' contributions	0	0
Actuarial (gain) loss	(187)	99
Benefits paid	(166)	(170)
Foreign currency translation and other	(7)	10
Settlements	(16)	(22)
Balance at end of period	2,466	2,749	2,729
Change in plan assets:
Balance beginning of period	2,261	2,193
Actual return on plan assets	(69)	221
Company contributions	23	29
Participants' contributions	0	0
Benefits paid	(166)	(170)
Foreign currency translation and other	(8)	10
Settlements	(16)	(22)
Balance end of period	2,025	2,261	2,193
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status	(441)	(488)
Amounts recognized on the Consolidated Balance Sheets as of December 31:
Other assets	9	4
Other liabilities	(450)	(492)
Net amount recognized	(441)	(488)
Amounts recognized in Accumulated other comprehensive income, not yet recognized in net periodic cost (benefit):
Prior service credit	0	0
Net actuarial (gain) loss	984	987
Net amount recognized	984	987
Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance at beginning of period	11	15
Service cost	0	0	0
Interest cost	0	0
Participants' contributions	3	4
Actuarial (gain) loss	0	(1)
Benefits paid	(5)	(7)
Foreign currency translation and other	0	0
Settlements	0	0
Balance at end of period	9	11	15
Change in plan assets:
Balance beginning of period	0	0
Actual return on plan assets	0	0
Company contributions	2	3
Participants' contributions	3	4
Benefits paid	(5)	(7)
Foreign currency translation and other	0	0
Settlements	0	0
Balance end of period	0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]
Funded status	(9)	(11)
Amounts recognized on the Consolidated Balance Sheets as of December 31:
Other assets	0	0
Other liabilities	(9)	(11)
Net amount recognized	(9)	(11)
Amounts recognized in Accumulated other comprehensive income, not yet recognized in net periodic cost (benefit):
Prior service credit	0	(2)
Net actuarial (gain) loss	(3)	(4)
Net amount recognized	$ (3)	$ (6)