Income Taxes - Summary of Operating Loss Carryforwards (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 172	[1]
Deferred Tax Assets, Operating Loss Carryforwards	37
Deferred Tax Assets, Tax Credit Carryforwards	31
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	10,813	[1]
Deferred Tax Assets, Operating Loss Carryforwards	858
Deferred Tax Assets, Tax Credit Carryforwards	29
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	605	[1]
Deferred Tax Assets, Operating Loss Carryforwards	163
Deferred Tax Assets, Tax Credit Carryforwards	0
Income Tax Authority, Name [Domain]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	11,590	[1]
Deferred Tax Assets, Operating Loss Carryforwards	1,058
Deferred Tax Assets, Tax Credit Carryforwards	$ 60
Minimum [Member] | Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2023
Tax Credit Carryforward, Expiration Date	Dec. 31, 2023
Minimum [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2017
Tax Credit Carryforward, Expiration Date	Dec. 31, 2016
Maximum [Member] | Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2025
Maximum [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2036

[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 2023.