Employee Retirement Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Matching contributions for 401(k) plan and Top Hat savings plan	$ 2		$ 2	$ 7	$ 7
Pension Contributions		15
Qualified Pension Plans [Member] | Future Period [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected contribution by employer for the remainder of the year	$ 0		$ 0	$ 0	$ 0