Significant business acquisitions - Narrative (Detail) (USD $)	3 Months Ended	12 Months Ended		0 Months Ended			0 Months Ended	2 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Dec. 19, 2013 NV Energy [Member]	Dec. 19, 2013 NV Energy [Member] Berkshire Hathaway Energy [Member]	Jan. 02, 2014 IMI plc Beverage Dispensing and Merchandising Operations [Member] Marmon [Member]	Feb. 25, 2014 Lubrizol Specialty Products Inc. (formerly Phillips Specialty Products Inc.) [Member]	Feb. 25, 2014 Lubrizol Specialty Products Inc. (formerly Phillips Specialty Products Inc.) [Member] PSX [Member]	Feb. 25, 2014 IMI plc and LSPI [Member]	Mar. 31, 2014 IMI plc and LSPI [Member]
Business Acquisition [Line Items]
Aggregate consideration paid for acquisitions				$ 5,600,000,000	$ 1,130,000,000
Percentage of acquiree's common stock acquired						100.00%
Number of shares exchanged							17,422,615
Fair value of shares exchanged	1,350,000,000						1,350,000,000
Preliminary fair values of identified assets			14,393,000,000						1,870,000,000
Preliminary fair values of identified liabilities			8,797,000,000						450,000,000
Residual goodwill	$ 1,236,000,000	$ 2,732,000,000						$ 1,060,000,000