Employee Benefit Plans (Change in Fair Value of Company's Level 3 Pension Assets) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	$ 2,618
End balance	2,965	$ 2,618
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	795	1,002
Realized gains/(losses)	53	(10)
Unrealized losses	8	(28)
Transfers out, net	(22)	(137)
Foreign currency losses	1	(32)
End balance	835	795
Level 3 | Real Estate
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	137	138
Realized gains/(losses)	18	9
Unrealized losses	(7)	0
Transfers out, net	(27)	(6)
Foreign currency losses	2	(4)
End balance	123	137
Level 3 | Other Debt Securities
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	359	418
Realized gains/(losses)	38	(29)
Unrealized losses	0	0
Transfers out, net	(12)	(12)
Foreign currency losses	(8)	(18)
End balance	377	359
Level 3 | Hedge Funds and Other Assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning balance	299	446
Realized gains/(losses)	(3)	10
Unrealized losses	15	(28)
Transfers out, net	17	(119)
Foreign currency losses	7	(10)
End balance	$ 335	$ 299