Employee Retirement Plans - Net Periodic Pension Cost for Defined Benefit Pension 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 Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost
Interest cost	2	2	3	3
Expected return on plan assets
Amortization of net loss			1	1
Net periodic pension cost	2	2	4	4
Qualified Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	1	1	2	3
Interest cost	10	10	20	20
Expected return on plan assets	(9)	(9)	(18)	(17)
Amortization of net loss	4	4	8	7
Net periodic pension cost	$ 6	$ 6	$ 12	$ 13