Income Tax - Components of Provision for Tax on Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal, current	$ 154	$ 176	$ 135
State, current	2	3	4
Income Tax Current	156	179	139
Deferred:
Federal, deferred	(128)	(139)	(83)
Income Tax Deferred	$ 28	$ 40	$ 56