Income Taxes - Related Party Income Taxes (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Long-term income tax receivable		$ 658	$ 530
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%	21.00%	35.00%
Parent Company [Member]
Related Party Transaction [Line Items]
Income Taxes Receivable From (Payable To) Related Parties Current		$ 13	$ 76
Long-term income tax receivable		658	530
State and Local Jurisdiction [Member]
Related Party Transaction [Line Items]
Operating Loss Carryforwards	[1]	7,190
Iowa Senate File 2417, Rate Effective Starting 2021 [Member] | State and Local Jurisdiction [Member]
Related Party Transaction [Line Items]
Operating Loss Carryforwards		$ 138	$ 79

[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.