Restructuring - Charges and Spending Relating to Merger Restructuring Program and 2008 Restructuring Program Activities (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
Restructuring Cost and Reserve [Line Items]
Expense	$ 163	$ 275	$ 741	$ 1,201
Merger Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserves January 1, 2012			1,195
Expense	150	255	718	1,176
(Payments) receipts, net			(873)
Non-cash activity			(257)
Restructuring reserves September 30, 2012	783		783
2008 Global Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserves January 1, 2012			126
Expense	13	20	23	25
(Payments) receipts, net			(27)
Non-cash activity			(27)
Restructuring reserves September 30, 2012	95		95
Separation Costs [Member]
Restructuring Cost and Reserve [Line Items]
Expense	58	68	351	667
Separation Costs [Member] | Merger Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserves January 1, 2012			1,144
Expense	59	63	363	670
(Payments) receipts, net			(742)
Restructuring reserves September 30, 2012	765		765
Separation Costs [Member] | 2008 Global Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserves January 1, 2012			126
Expense	(1)	5	(12)	(3)
(Payments) receipts, net			(19)
Restructuring reserves September 30, 2012	95		95
Accelerated Depreciation [Member]
Restructuring Cost and Reserve [Line Items]
Expense	32	140	193	423
Accelerated Depreciation [Member] | Merger Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Expense	25	130	183	407
Non-cash activity			(183)
Accelerated Depreciation [Member] | 2008 Global Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Expense	7	10	10	16
Non-cash activity			(10)
Other [Member]
Restructuring Cost and Reserve [Line Items]
Expense	73	67	197	111
Other [Member] | Merger Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring reserves January 1, 2012			51
Expense	66	62	172	99
(Payments) receipts, net			(131)
Non-cash activity			(74)
Restructuring reserves September 30, 2012	18		18
Other [Member] | 2008 Global Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Expense	7	5	25	12
(Payments) receipts, net			(8)
Non-cash activity			$ (17)