Condensed Financial Information - Statements of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net earnings	$ 10,254	$ 12,967	$ 8,055
Adjustments to reconcile net earnings to cash flows from operating activities:
Income taxes payable	1,493	2,348	2,035
Other noncash adjustments	(811)	(255)	149
Net cash flows from operating activities	20,476	17,895	15,846
Cash flows from investing activities:
Purchases of fixed maturity securities	(7,362)	(9,819)	(10,798)
Sales of fixed maturity securities	3,353	5,435	4,338
Net cash flows from investing activities	(19,189)	(18,277)	(11,161)
Cash flows from financing activities:
Net cash flows from financing activities	(2,217)	8,125	233
Increase in cash and cash equivalents	(928)	7,669	5,019
Cash and cash equivalents at beginning of year	38,227	30,558	25,539
Cash and cash equivalents at end of year	37,299	38,227	30,558
Other cash flow information:
Income taxes paid	2,885	3,547	2,032
Berkshire Hathaway (Parent) [Member]
Cash flows from operating activities:
Net earnings	10,254	12,967	8,055
Adjustments to reconcile net earnings to cash flows from operating activities:
Undistributed earnings of subsidiaries	(4,546)	(8,546)	(5,045)
Income taxes payable	69	34	102
Other noncash adjustments	70	31	(12)
Net cash flows from operating activities	5,847	4,486	3,100
Cash flows from investing activities:
Purchases of fixed maturity securities		(98)	(200)
Sales of fixed maturity securities	298		127
Investments in and advances to subsidiaries	(3,633)	(11,929)	(4)
Net cash flows from investing activities	(3,335)	(12,027)	(77)
Cash flows from financing activities:
Proceeds from borrowings	2,021	8,137	196
Repayments of borrowings	(2,094)	(117)	(100)
Purchases of noncontrolling interests	(1,811)	(1)	(19)
Other financing activities	45	153	(28)
Net cash flows from financing activities	(1,839)	8,172	49
Increase in cash and cash equivalents	673	631	3,072
Cash and cash equivalents at beginning of year	6,616	5,985	2,913
Cash and cash equivalents at end of year	7,289	6,616	5,985
Other cash flow information:
Income taxes paid	1,882	2,325	1,203
Interest paid	$ 122	$ 69	$ 6