Retirement Plans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Non Qualified
Defined Benefit Plan Disclosure [Line Items]
Benefits paid			$ 9
United States Pension Plans of US Entity, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	47	37	95	75
Interest cost	143	153	287	298
Expected return on plan assets	(182)	(189)	(364)	(373)
Actuarial loss	122	78	244	154
Amortization of prior service cost	9	8	17	16
Net periodic benefit expense	$ 139	$ 87	$ 279	$ 170