Retirement Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan expected contributions for next year	$ 1
Contribution under plan	31	31
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan expected contributions for next year	15
Contribution under plan	13	13
Profit Sharing Plan
Defined Benefit Plan Disclosure [Line Items]
Contribution under plan	11	11	11
Maximum contribution as percentage of participants' earnings	15.00%
Savings Plan
Defined Benefit Plan Disclosure [Line Items]
Contribution under plan	$ 5	$ 5	$ 5
Employer matching contribution to plan	Provides a matching contribution of 100% of the first 3% of pay contributed and 50% of the next 2% of pay contributed by employees.
Savings Plan | First 3% of pay contributed
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution percentage	100.00%
Savings Plan | Next 2% of pay contributed
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution percentage	50.00%