Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ (10)	$ 17	$ 12	$ 109
Pension and Other Postretirement Benefits Costs Charged to Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Pension benefits costs			$ 6		$ 16
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					97
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 26