Employee Benefit Plans - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Long Term Incentive Deferred Cash Expense	$ 39	$ 36
Common Stock, Capital Shares Reserved for Future Issuance	21
Share Based Compensation Arrangement By Share Based Payment Award Options Available For Additional Grant	17
Share Based Compensation Arrangement By Share Based Payment Award Restricted Stock Available For Additional Grant	9
Fair value of options granted per share	$ 7.37	$ 7.83
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	8	9
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	8
Defined Benefit Plan, Contributions by Employer	1
Contributed To Postretirement Welfare Plan	1
Expected Medicare Subsidy Reimbursement Amount	$ 3
Pension Plans, Defined Benefit
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Expected Long Term Return on Assets	7.00%
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Expected Long Term Return on Assets	5.00%
Restricted Stock [Member]
Common Stock, Capital Shares Reserved for Future Issuance	17