Acquisitions, Divestitures, Goodwill and Intangible Assets - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 business Segment	Dec. 31, 2011 business	Dec. 31, 2010 business
Acquisitions Divestitures Intangible Assets And Goodwill [Line Items]
Number of Reporting Units Where Estimated Fair Value is Greater than Respective Book Value			3
Number of businesses acquired			7	6	3
Acquisition of business, aggregate value			$ 444	$ 1,560	$ 233
Amortization expense	234	238	234	238	224
Other Income [Member]
Acquisitions Divestitures Intangible Assets And Goodwill [Line Items]
Pretax gain on sale of detection systems reported in other income				$ 38