Employee Retirement Plans - Information about Plan Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Qualified Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Projected benefit obligation	$ 1,056	$ 943
Accumulated benefit obligation	1,054	941
Fair value of plan assets	594	504
Non-Qualified Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Projected benefit obligation	181	174
Accumulated benefit obligation	$ 181	$ 174

If aggregate disclosures are presented, the aggregate pension accumulated benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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If aggregate disclosures are presented, the aggregate fair value of plan assets for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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- Definition

If aggregate disclosures are presented, the aggregate projected benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

+ References+ Details