Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			$ 30		$ 291
Restructuring and other charges	$ 23	$ 217	116	$ 394
Pension And Other Postretirement Benefits Costs Charged To Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost					35
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			7	45	76
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges				$ 29	$ 86
Pension Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			1
Restructuring and other charges	$ 2		$ 2