Employee Benefits - Net Pension Cost and the Amount Recognized in OCI for All Funded and Unfunded Plans (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	$ 7	$ 13
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on PBO	47	57	60
Expected return on plan assets	(70)	(81)	(72)
Amortization of losses	16	11	12
Net pension cost	(7)	(13)
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	63	120	54
Amortization of losses	(16)	(11)	(12)
Total recognized in comprehensive income	47	109	42
Total recognized in net pension cost and comprehensive income	$ 40	$ 96	$ 42