Accumulated Other Comprehensive Loss - Change in Accumulated Other Comprehensive Loss Balances (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Accumulated Other Comprehensive Income Loss [Line Items]
Net Unrealized Gains (Losses) on Cash Flow Hedges, Beginning Balance			$ (17)	$ (21)
Net Unrealized Gains (Losses) on Cash Flow Hedges, Change during the period	21	(3)	41	(3)
Net Unrealized Gains (Losses) on Cash Flow Hedges, Ending Balance	24	(24)	24	(24)
Net Unrealized Gains (Losses) on Securities, Beginning Balance			(107)	(238)
Net Unrealized Gains (Losses) on Securities, Change during the period	195	54	281	96
Net Unrealized Gains (Losses) on Securities, Ending Balance	174	(142)	174	(142)
Foreign Currency Translation Adjustment, Beginning Balance				1
Foreign Currency Translation Adjustment, Change during the period	1	(2)	1	(1)
Foreign Currency Translation Adjustment, Ending Balance	1		1
Pension and Other Benefits Adjustment, Beginning Balance			(685)	(419)
Pension and Other Benefits Adjustment, Change during the period	16	8	46	29
Pension and Other Benefits Adjustment, Ending Balance	(639)	(390)	(639)	(390)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance			(809)	(677)
Accumulated Other Comprehensive Income Loss, Change during the period	233	57	369	121
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (440)	$ (556)	$ (440)	$ (556)