Employee Benefit Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Age	Dec. 31, 2011	Dec. 31, 2010
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Net actuarial losses	$ (13)	$ (20)	$ (4)
Net actuarial losses amortization of net actuarial loss	2
Unrecognized actuarial losses, included in accumulated other comprehensive (loss) income	98
Unrecognized actuarial losses, included in accumulated other comprehensive (loss) income, net of tax	86
Unfunded status	57
Approximate time period considered for investment performance to determine expected return on plan assets (in years)	10 Years
Expected contribution to plans	14
Minimum age for participation of employees in 401(k)plan	21
Contribution by each participant of defined contribution plans on a pretax basis to the plan subject to certain maximum limits	Each participant may contribute on a pretax basis between 1% and 50% of his or her eligible compensation to the plan subject to certain maximum limits
Eligible employees enrollment	After 90 days
Minimum period of service for provide matching contribution to employee	1 year
Defined contribution plan, cost recognized	16	15	13
Balance of publicly traded common stock defined contribution plan	69	67
Collective bargaining agreement expiration date	Jun. 30, 2019
Maximum contributions by employer	less than 5%	less than 5%	less than 5%
Health care contributions	24	26	27
Debt securities [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Target asset allocation in debt securities	63.00%
Equity securities [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Target asset allocation in debt securities	36.00%
Other [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Target asset allocation in debt securities	1.00%
Assumptions [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Assumed annual rate of increase in the per capita cost of covered health care benefits	9.00%
Assumed ultimate annual rate increase of per capita cost of covered health	5.00%
Effect of one-percentage point change in assumed health care cost trend rates on postretirement benefit obligation	1
Other Liabilities [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Unfunded status	76
Accrued expenses [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Unfunded status	3
Other Assets [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Unfunded status	22
Scenario, Forecast [Member]
Under Funded Status Of Plans Balance Sheet Location [Line Items]
Actuarial loss expected to be recognized in net periodic pension cost	3
Actuarial loss expected to be recognized in net periodic pension cost, net of tax	$ 2