Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Effects of a 1% Change in the Assumed Health Care Cost Trend Rate Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Effect of a 1% increase on total of service and interest cost components	$ 3
Effect of a 1% increase on other postretirement benefit obligation	23
Effect of a 1% decrease on total of service and interest cost components	(2)
Effect of a 1% decrease on other postretirement benefit obligation	$ (20)