Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			$ 112	$ 246
Restructuring and other charges	$ 217	$ 110	394	571
Pension Costs [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost				26
Pension And Other Postretirement Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Other layoff cost including reclassification in pension cost			13
Asset Retirement Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			45	95
Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 29	$ 47