Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Curtailment gains included in accumulated other comprehensive income (loss)		$ 18
Curtailment gain	$ 0	2	$ 0	$ 2	$ 0
Total service costs	10		13	34	41
Total interest costs	24		25	71	77
Total amortization of unrecognized net actuarial losses	(8)		(13)	(29)	(46)
Total expected return on plan assets	49		42	147	125
Net non-service pension (income) costs included in Other, net	(17)		$ 0	(49)	$ 9
Corporation's estimated contribution for funded pension plans during the current year	$ 47			47
Corporation's contribution for funded pension plan during the year to date				$ 35
U.S. Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Total decrease in post retirement liabilities		$ (125)
Scenario, Forecast
Defined Benefit Plan Disclosure [Line Items]
Total service costs						$ 45
Net non-service pension costs						60
Total interest costs						95
Total amortization of unrecognized net actuarial losses						40
Total expected return on plan assets						$ 195