Income Taxes - Summary of Operating Loss Carryforwards (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Current Income Tax Expense (Benefit)		$ 1,572	$ 888	$ 591
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	[1]	302
Deferred Tax Assets, Operating Loss Carryforwards		63
Deferred Tax Assets, Tax Credit Carryforwards		15
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	[1]	7,190
Deferred Tax Assets, Operating Loss Carryforwards		409
Deferred Tax Assets, Tax Credit Carryforwards		28
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	[1]	704
Deferred Tax Assets, Operating Loss Carryforwards		162
Deferred Tax Assets, Tax Credit Carryforwards		0
Income Tax Authority, Name [Domain]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	[1]	8,196
Deferred Tax Assets, Operating Loss Carryforwards		634
Deferred Tax Assets, Tax Credit Carryforwards		$ 43

[1] The federal net operating loss carryforwards relate principally to net operating loss carryforwards of subsidiaries that are tax residents in both the United States and the United Kingdom. The federal net operating loss carryforwards were generated prior to Berkshire Hathaway Inc.'s ownership and will begin to expire in 2021.