Supplemental cash flow information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for income taxes	$ 283	$ 241
Investments in equity securities exchanged in connection with business acquisition	1,350
Liabilities assumed in connection with business acquisitions	567
Insurance and Other [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	139	119
Railroad, Utilities and Energy [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	678	505
Finance and Financial Products [Member]
Supplemental Cash Flow Information [Line Items]
Cash paid during the period for interest	$ 102	$ 139