Accumulated Other Comprehensive Loss - Change in Accumulated Other Comprehensive Loss Balances (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Net Unrealized Gains (Losses) on Cash Flow Hedges, Beginning Balance	$ 24	$ (17)
Net Unrealized Gains (Losses) on Cash Flow Hedges, Other comprehensive income before reclassifications	6	23
Net Unrealized Gains (Losses) on Cash Flow Hedges, Amounts reclassified from accumulated other comprehensive loss	(9)	(3)
Net Unrealized Gains (Losses) on Cash Flow Hedges, Ending Balance	21	3
Net Unrealized Gains (Losses) on Securities, Beginning Balance	159	(107)
Net Unrealized Gains (Losses) on Securities, Other comprehensive income before reclassifications	(320)	115
Net Unrealized Gains (Losses) on Securities, Amounts reclassified from accumulated other comprehensive loss	(74)	(29)
Net Unrealized Gains (Losses) on Securities, Ending Balance	(235)	(21)
Foreign Currency Translation Adjustment, Beginning Balance	1
Foreign Currency Translation Adjustment, Other comprehensive income before reclassifications	(3)
Foreign Currency Translation Adjustment, Ending Balance	(2)
Pension and Other Benefits Adjustment, Beginning Balance	(698)	(685)
Pension and Other Benefits Adjustment, Amounts reclassified from accumulated other comprehensive loss	(35)	(30)
Pension and Other Benefits Adjustment, Ending Balance	(663)	(655)
Accumulated Other Comprehensive Loss, Beginning Balance	(514)	(809)
Accumulated Other Comprehensive Loss, Other comprehensive income before reclassifications	(317)	138
Accumulated Other Comprehensive Loss, Amounts reclassified from accumulated other comprehensive loss	(48)	(2)
Accumulated Other Comprehensive Loss, Ending Balance	$ (879)	$ (673)