Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Expense) Table (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit cost
Service cost	$ 85	$ 76	$ 78
Interest cost	78	85	85
Expected return on plan assets	(91)	(91)	(85)
Amortization of net actuarial loss (gain)	118	93	85
Amortization of net prior service cost (credit)	0	0	2
Settlement loss	14	0	0
Net periodic benefit cost	204	163	165
Amounts recognized in other comprehensive income (expense)
Net actuarial gain (loss)	342	(156)	(183)
Amortization of net actuarial (gain) loss	118	93	85
Net prior service (cost) credit	0	0	12
Amortization of net prior service cost (credit)	0	0	2
Settlement loss	14	0	0
Total amounts recognized in other comprehensive income (expense)	474	(63)	(84)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic benefit cost
Service cost	9	9	9
Interest cost	14	16	16
Expected return on plan assets	0	0	0
Amortization of net actuarial loss (gain)	0	0	0
Amortization of net prior service cost (credit)	1	2	0
Settlement loss	0	0	0
Net periodic benefit cost	24	27	25
Amounts recognized in other comprehensive income (expense)
Net actuarial gain (loss)	74	1	(30)
Amortization of net actuarial (gain) loss	0	0	0
Net prior service (cost) credit	0	0	0
Amortization of net prior service cost (credit)	1	2	0
Settlement loss	0	0	0
Total amounts recognized in other comprehensive income (expense)	$ 75	$ 3	$ (30)