Change in Plan Assets (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Pension Plans, Defined Benefit
Defined Benefit Plan, Benefits Paid, Net	$ 165	[1]	$ 181	[1]
Defined Benefit Plan, Fair Value of Plan Assets	2,873	[1],[2]	2,742	[1]
Defined Benefit Plan, Actual Return on Plan Assets	371	[1]	309	[1]
Defined Benefit Plan, Contributions by Employer	6	[1]	8	[1]
Defined Benefit Plan, Contributions by Plan Participants	0	[1]	0	[1]
Defined Benefit Plan, Benefits Paid	(165)	[1]	(181)	[1]
Defined Benefit Plan, Fair Value of Plan Assets	3,080	[1],[2]	2,873	[1],[2]
Defined Benefit Plan, Administration Expenses	5	[1]	5	[1]
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Benefits Paid, Net	16	[3]	38	[3]
Defined Benefit Plan, Fair Value of Plan Assets	158	[3],[4]	164	[3]
Defined Benefit Plan, Actual Return on Plan Assets	8	[3]	14	[3]
Defined Benefit Plan, Contributions by Employer	0	[3]	0	[3]
Defined Benefit Plan, Contributions by Plan Participants	11	[3]	21	[3]
Defined Benefit Plan, Benefits Paid	(17)	[3]	(41)	[3]
Defined Benefit Plan, Fair Value of Plan Assets	160	[3],[4]	158	[3],[4]
Defined Benefit Plan, Administration Expenses	$ 0	[3]	$ 0	[3]

[1] 1 Employer contributions represent the benefits that were paid to nonqualified plan participants. SERPs are not funded through plan assets.

[2] 4 Includes $1 million and $0, of the Company's common stock acquired by the asset manager and held as part of the equity portfolio for pension benefits at December 31, 2014 and 2013, respectively.

[3] 2 Plan remeasured at December 31, 2013 due to plan amendment.

[4] 1 Fair value measurements do not include accrued income.