Significant Business Acquisitions (Detail) (USD $)	3 Months Ended		6 Months Ended					3 Months Ended	43 Months Ended		3 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Feb. 12, 2010	Feb. 12, 2010 Class A [Member] Burlington Northern Santa Fe [Member]	Feb. 12, 2010 Class B [Member] Burlington Northern Santa Fe [Member]	Mar. 31, 2010 Burlington Northern Santa Fe [Member]	Feb. 11, 2010 Burlington Northern Santa Fe [Member]	Feb. 12, 2010 Burlington Northern Santa Fe [Member]	Mar. 31, 2011 Marmon Holdings [Member]	Dec. 31, 2010 Marmon Holdings [Member]	Dec. 31, 2010 The Lubrizol Corporation [Member]	Mar. 13, 2011 The Lubrizol Corporation [Member]	Jun. 30, 2011 Class B [Member] Wesco Financial Corporation [Member]	Jun. 30, 2011 Wesco Financial Corporation [Member]
Business Acquisition [Line Items]
Acquisition of remaining common stock outstanding, shares										264,500,000
Acquisition of common stock outstanding, percentage										77.50%	16.50%
Aggregate consideration for acquisition of common stock outstanding, amount										$ 26,500,000,000
Acquisition of common stock outstanding, paid in cash										15,900,000,000	1,500,000,000
Percentage of shares owned after stock transaction									22.50%		80.20%
Excess of the consideration over noncontrolling interest												600,000,000
Acquisition paid in common stock, shares						80,931	20,976,621								3,250,000
Percentage of acquisition funded through existing cash balances, percentage					50.00%
Percentage of acquisition funded through new debt, percentage					50.00%
Shares owned prior to acquisition, shares									76,800,000
Equity method investment carrying value prior to investment in subsidiaries										6,600,000,000
Holding gain recognized for the difference between the fair value and carrying value of shares held under the equity method								1,000,000,000
Common stock to be acquired in a business acquisition (dollars per share)														$ 135
Aggregate cash consideration to be paid for an acquisition, amount														9,000,000,000
Revenues													5,400,000,000
Net earnings	3,417,000,000	1,968,000,000	4,928,000,000	5,601,000,000									732,000,000
Aggregate consideration for noncontrolling interest acquisition, amount																543,000,000
Aggregate cash consideration paid for noncontrolling interest acquisiton, amount																$ 298,000,000