Pension Plans Postretirement and Other Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	12 Months Ended			3 Months Ended
	Jan. 02, 2012 retirement_plan	Dec. 31, 2014 retiree	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014
Pension and Other Postretirement Benefits Disclosure [Line Items]
Pension benefit obligations		$ 931	$ 931
Pension benefit obligations with funding requirements		879	879
Pension Fund assets available to fund pension benefit obligations		726	726
Pension benefit obligations with no funding requirements		52	52
Acceptable tolerance limit of investment allocations for securities			5.00%
Employer contributions			46
Expected contributions in 2013			31
Minimum retirement age for eligible employees of the post retirement plans			55 years
Minimum years of service for eligible employees of the post retirement plans			10 years
Prior period correction		11
Defined Benefit Plan, Prior Period Adjustment, Number of Retirees Entitled to Benefits Not Included		170
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate			6.50%	7.00%	7.50%
Defined Benefit Plan Ultimate Health Care Cost Year Five			4.50%	4.50%	4.50%
Retirement Savings Plan	1
Maximum percentage of salary deferral allowed under the Employee Stock Ownership Plans		75.00%	75.00%
Defined Compensation Plan, Amended Employee Match Percentage on One Hundred Percent of Employee Contributions			3.00%
Defined Compensation Plan, Amended Employee Match Percentage on Fifty Percent of Employee Contributions			50.00%
Expense recorded relating to employee matching contribution			25	23	21
Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Defined Compensation Plan, Amended Employee Match Percentage on Fifty Percent of Employee Contributions			5.00%
Postretirement
Pension and Other Postretirement Benefits Disclosure [Line Items]
Employer contributions			8	8
Percent of eligible employees who participated in voluntary buyout, more than						60.00%
Prior period correction			15
One percentage point increase effect on postretirement benefit obligation			15
One percentage point decrease effect on postretirement benefit obligation			12
Postretirement | Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Defined benefit plan effect of one percentage point increase on service and interest cost components			1
Defined benefit plan effect of one percentage point decrease on service and interest cost components			1
Pension Plans, Defined Benefit
Pension and Other Postretirement Benefits Disclosure [Line Items]
Expected contributions in 2013			$ 9
Equity Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Targeted pension plan allocations in debt securities			70.00%
Debt Securities
Pension and Other Postretirement Benefits Disclosure [Line Items]
Targeted pension plan allocations in debt securities			30.00%
Postretirement | Minimum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Defined Compensation Plan, Amended Employee Match Percentage on One Hundred Percent of Employee Contributions			100.00%
Defined Compensation Plan, Amended Employee Match Percentage on Fifty Percent of Employee Contributions			3.00%