Income Taxes - Schedule of Expiration Periods of Deferred Tax Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Tax Credit Carryforward [Line Items]
Tax loss carryforwards	$ 2,186
Tax credit carryforwards	508
Other	3,708
Valuation allowance	(1,400)
Deferred tax assets, net	5,002	4,650
Expires Within 10 Years [Member]
Tax Credit Carryforward [Line Items]
Tax loss carryforwards	332
Tax credit carryforwards	370
Other
Valuation allowance	(212)
Deferred tax assets, net	490
Expires Within 11-20 Years [Member]
Tax Credit Carryforward [Line Items]
Tax loss carryforwards	886
Tax credit carryforwards	73
Other
Valuation allowance	(659)
Deferred tax assets, net	300
No Expiration [Member]
Tax Credit Carryforward [Line Items]
Tax loss carryforwards	968
Tax credit carryforwards	65
Other	762
Valuation allowance	(244)
Deferred tax assets, net	1,551
Other [Member]
Tax Credit Carryforward [Line Items]
Tax loss carryforwards
Tax credit carryforwards
Other	2,946
Valuation allowance	(285)
Deferred tax assets, net	$ 2,661