Notes payable and other borrowings - Narrative (Detail) € in Millions, £ in Millions, $ in Millions, ¥ in Billions	1 Months Ended				9 Months Ended
	Sep. 30, 2019 JPY (¥)	Jul. 31, 2019 USD ($)	Jun. 30, 2019 GBP (£)	Jan. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 JPY (¥)	Sep. 30, 2019 GBP (£)	Sep. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Insurance and Other [Member]
Debt Instrument [Line Items]
Carrying value of notes					$ 37,176					$ 34,975
Insurance and Other [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Carrying value of notes							¥ 430.0	£ 1,750	€ 6,850
Insurance and Other [Member] | Berkshire Hathaway Inc. (Parent) [Member] | Subsidiaries Excluding Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Guarantee obligation					$ 1,300
Insurance and Other [Member] | Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage					4.00%		4.00%	4.00%	4.00%
Insurance and Other [Member] | Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year					2019
Insurance and Other [Member] | Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year					2045
Insurance and Other [Member] | Senior Notes [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 430.0
Gains attributable to changes in foreign currency exchange rates					$ 447	$ 273
Insurance and Other [Member] | Senior Notes [Member] | Subsidiaries [Member] | Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | £			£ 1,750
Repayments of borrowings					$ 3,950
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2024 at 0.17% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 108.5
Debt instrument, interest rate, stated percentage					0.17%		0.17%	0.17%	0.17%
Debt maturity year	2024
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2026 at 0.27% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 61.0
Debt instrument, interest rate, stated percentage					0.27%		0.27%	0.27%	0.27%
Debt maturity year	2026
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2029 at 0.44% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 146.5
Debt instrument, interest rate, stated percentage					0.44%		0.44%	0.44%	0.44%
Debt maturity year	2029
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2034 at 0.787% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 19.0
Debt instrument, interest rate, stated percentage					0.787%		0.787%	0.787%	0.787%
Debt maturity year	2034
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2039 at 0.965% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 59.0
Debt instrument, interest rate, stated percentage					0.965%		0.965%	0.965%	0.965%
Debt maturity year	2039
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2049 at 1.108% [Member] | Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | ¥	¥ 36.0
Debt instrument, interest rate, stated percentage					1.108%		1.108%	1.108%	1.108%
Debt maturity year	2049
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2049 at 4.25% [Member] | Subsidiaries [Member] | Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 2,000
Debt instrument, interest rate, stated percentage				4.25%
Debt maturity year				2049
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2039 at 2.375% [Member] | Subsidiaries [Member] | Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | £			£ 1,000
Debt instrument, interest rate, stated percentage			2.375%
Debt maturity year			2039
Insurance and Other [Member] | Senior Notes [Member] | Notes Due 2059 at 2.625% [Member] | Subsidiaries [Member] | Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued | £			£ 750
Debt instrument, interest rate, stated percentage			2.625%
Debt maturity year			2059
Railroad, Utilities and Energy [Member]
Debt Instrument [Line Items]
Carrying value of notes					$ 65,018					$ 62,515
Railroad, Utilities and Energy [Member] | Debt Due 2029 To 2050 [Member] | Subsidiaries [Member] | Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Principal amount of debt issued					$ 3,400
Weighted average interest rate, percentage					3.90%		3.90%	3.90%	3.90%
Railroad, Utilities and Energy [Member] | Debt Due 2029 To 2050 [Member] | Subsidiaries [Member] | Berkshire Hathaway Energy and Subsidiaries [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year					2029
Railroad, Utilities and Energy [Member] | Debt Due 2029 To 2050 [Member] | Subsidiaries [Member] | Berkshire Hathaway Energy and Subsidiaries [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year					2050
Railroad, Utilities and Energy [Member] | Senior Unsecured Debenture [Member] | Debentures Due in 2050 [Member] | Subsidiaries [Member] | BNSF [Member]
Debt Instrument [Line Items]
Principal amount of debt issued		$ 825
Debt instrument, interest rate, stated percentage		3.55%
Debt maturity year		2050