Employee Benefit Plans (Change in Fair Value of Company's Level 3 Pension Assets) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	$ 2,883
End balance	2,618	$ 2,883
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	1,002	515
Realized gains	(10)	59
Unrealized losses	(28)	5
Transfers (out)/in, net	(137)	386
Foreign currency losses	(32)	37
End balance	795	1,002
Level 3 | Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	138	129
Realized gains	9	11
Unrealized losses	0	0
Transfers (out)/in, net	(6)	(5)
Foreign currency losses	(4)	3
End balance	137	138
Level 3 | Other Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	418	16
Realized gains	(29)	45
Unrealized losses	0	0
Transfers (out)/in, net	(12)	355
Foreign currency losses	(18)	2
End balance	359	418
Level 3 | Hedge Funds and Other Assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	446	370
Realized gains	10	3
Unrealized losses	(28)	5
Transfers (out)/in, net	(119)	36
Foreign currency losses	(10)	32
End balance	$ 299	$ 446