Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Income Tax Examination, Year(s) under Examination	The Company's federal income tax returns are no longer subject to examination by the IRS for taxable years prior to 2006. The IRS audit of the 2006 federal income tax return is closed, but the return is still subject to examination to the extent of carryback claims. The Company's 2007 through 2009 federal income tax returns are currently under examination by the IRS. With limited exceptions, the Company is no longer subject to examinations by state and local taxing authorities for taxable years prior to 2006.
Income Tax Expense (Benefit)	$ 69	$ 33
Effective Income Tax Rate, Continuing Operations	22.00%	16.00%
Recognized a gross liability for interest related to its UTBs	22		21
Interest expense (income) related to UTBs	1	1
Gross cumulative unrecognized tax benefits	136		133
Amount that would affect the Company's effective tax rate, if recognized	91
Reasonably possible decrease in UTBs during the next 12 months	$ 90