Contingencies and Commitments - Narrative (Detail) - Investment Commitment [Member] - USD ($) $ / shares in Units, $ in Billions		6 Months Ended
	Apr. 30, 2019	Jun. 30, 2019
Contingencies and Commitments [Line Items]
Investment commitment description		On April 30, 2019, Berkshire committed to invest a total of $10 billion in connection with Occidental Petroleum Corporation’s (“Occidental”) proposal to acquire Anadarko Petroleum Corporation (“Anadarko”). The acquisition transaction between Occidental and Anadarko is subject to approval by Anadarko shareholders, who are scheduled to vote on the acquisition on August 8, 2019. If approved by Anadarko shareholders, we expect the acquisition and our investment will be completed shortly thereafter.   If completed, Berkshire’s investment will include newly issued Occidental Cumulative Perpetual Preferred Stock with an aggregate liquidation value of $10 billion, together with warrants to purchase up to 80 million shares of Occidental common stock at an exercise price of $62.50 per share. The preferred stock will accrue dividends at 8% per annum and will be redeemable at the option of Occidental commencing on the tenth anniversary of issuance at a redemption price equal to 105% of the liquidation preference plus any accumulated and unpaid dividends, or mandatorily under certain specified capital return events. Dividends will be paid in cash or, at Occidental’s option, in shares of Occidental common stock. The warrants issued with the preferred stock may be exercised in whole or in part until one year after the redemption of the preferred stock.
Occidental Petroleum Corporation [Member] | Cumulative Perpetual Preferred Stock and Warrants [Member]
Contingencies and Commitments [Line Items]
Investment commitment amount	$ 10
Occidental Petroleum Corporation [Member] | Cumulative Perpetual Preferred Stock [Member]
Contingencies and Commitments [Line Items]
Investment in preferred stock, liquidation value	$ 10
Investment in preferred stock, stated dividend rate	8.00%
Investment in preferred stock, period from issuance date to redemption period start date	10 years
Investment in preferred stock, redemption price percentage of liquidation preference	105.00%
Occidental Petroleum Corporation [Member] | Common Stock [Member]
Contingencies and Commitments [Line Items]
Number of common shares that can be purchased	80,000,000
Exercise price for warrants, per share	$ 62.50