Employee Retirement Plans - Net Periodic Pension Cost for Defined Benefit Pension Plans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Non-Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost
Interest cost	2	2	5	5
Expected return on plan assets
Amortization of net loss	1		2	1
Net periodic pension cost	3	2	7	6
Qualified Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	3	4
Interest cost	9	13	29	33
Expected return on plan assets	(9)	(10)	(27)	(27)
Amortization of net loss	4	3	12	10
Net periodic pension cost	$ 5	$ 7	$ 17	$ 20