Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Parenthetical) (Detail) - Other Income [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Energy Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings	$ 50	$ 50
Interest Rate Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings		7
Nickel Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings	$ 50	$ 50