Supplemental cash flow information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for income taxes	$ 2,151	$ 2,724
Investments in equity securities exchanged in connection with business acquisitions	2,478
Liabilities assumed in connection with business acquisitions	1,038	4
Treasury stock acquired in connection with business acquisition	400
Insurance and Other [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	181	161
Railroad, Utilities and Energy [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	1,209	918
Finance and Financial Products [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	$ 237	$ 301