Reconciliation of Total Segment Operating Income to Consolidated Operating Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Unallocated items	$ (3,155)	$ (2,474)	$ (1,376)
Income from operations	12,760	11,742	10,381
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	$ 15,915	$ 14,216	$ 11,757