Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Restructuring and other charges	$ 18	$ 66	$ 134	$ 460
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Restructuring and other charges		$ 2	$ 2	$ 2