Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation for the pension plans	$ 2,381	$ 2,479
Estimated aggregate net actuarial loss and prior service cost to be amortized next year	34
Effect of one percent increase in health care cost trend rate on the accumulated other postretirement benefit obligation	67
Effect of one percent decrease in health care cost trend rate on the accumulated other postretirement benefit obligation	53
Effect of one percent increase in health care cost trend rate on net other postretirement benefit cost	6
Effect of one percent decrease in health care cost trend rate on net other postretirement benefit cost	5
Employer annual elective matching contribution related to employee's eligible pre-tax contributions	Equal to 100%
The portion of employer annual elective matching contribution related to employee's eligible pre-tax contributions	Up to 4%
Employer contributions for Capital Accumulation Plan	29	26	27
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum range of portfolio allocation to equity securities	55.00%
Maximum range of portfolio allocation to equity securities	65.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	74	98
Fair value of plan assets invested in pooled funds	1,425	1,200
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	10	10
Fair value of plan assets invested in pooled funds	$ 130	$ 96