Supplemental cash flow information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for income taxes	$ 4,028	$ 2,896
Non-cash investing activity - liabilities assumed in connection with business acquisitions	275	793
Insurance and Other [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	321	290
Railroad, Utilities and Energy [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	1,507	1,393
Finance and Financial Products [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	$ 401	$ 471