Condensed Financial Information - Statements of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net earnings attributable to Berkshire Hathaway shareholders	$ 14,824	$ 10,254	$ 12,967
Adjustments to reconcile net earnings to cash flows from operating activities:
Income taxes payable	1,710	1,493	2,348
Other noncash adjustments	(795)	(811)	(255)
Net cash flows from operating activities	20,950	20,476	17,895
Cash flows from investing activities:
Purchases of fixed maturity securities	(8,250)	(7,362)	(9,819)
Sales of fixed maturity securities	2,982	3,353	5,435
Net cash flows from investing activities	(10,574)	(19,189)	(18,277)
Cash flows from financing activities:
Acquisitions of treasury stock	(1,296)	(67)
Net cash flows from financing activities	(806)	(2,217)	8,125
Increase in cash and cash equivalents	9,693	(928)	7,669
Cash and cash equivalents at beginning of year	37,299	38,227	30,558
Cash and cash equivalents at end of year	46,992	37,299	38,227
Other cash flow information:
Income taxes paid	4,695	2,885	3,547
Berkshire Hathaway (Parent) [Member]
Cash flows from operating activities:
Net earnings attributable to Berkshire Hathaway shareholders	14,824	10,254	12,967
Adjustments to reconcile net earnings to cash flows from operating activities:
Undistributed earnings of subsidiaries	(8,301)	(4,546)	(8,546)
Income taxes payable	80	69	34
Other noncash adjustments	101	70	31
Net cash flows from operating activities	6,704	5,847	4,486
Cash flows from investing activities:
Purchases of fixed maturity securities			(98)
Sales of fixed maturity securities		298
Investments in and advances to subsidiaries	(1,525)	(3,633)	(11,929)
Net cash flows from investing activities	(1,525)	(3,335)	(12,027)
Cash flows from financing activities:
Proceeds from borrowings	1,740	2,021	8,137
Repayments of borrowings	(1,751)	(2,094)	(117)
Acquisitions of noncontrolling interests	(800)	(1,811)	(1)
Acquisitions of treasury stock	(1,296)	(67)
Other financing activities	196	112	153
Net cash flows from financing activities	(1,911)	(1,839)	8,172
Increase in cash and cash equivalents	3,268	673	631
Cash and cash equivalents at beginning of year	7,289	6,616	5,985
Cash and cash equivalents at end of year	10,557	7,289	6,616
Other cash flow information:
Income taxes paid	3,406	1,882	2,325
Interest paid	$ 180	$ 122	$ 69