Income Taxes Income Taxes - Tax Reform (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of Income Tax Expense (Benefit) [Line Items]
Current Income Tax Expense (Benefit)			$ (888)	$ (591)	$ (573)
Federal statutory income tax rate			21.00%	21.00%	35.00%
Deferred Tax Liabilities, Net			$ 9,653	$ 9,047
Regulatory Liabilities			7,311	7,506
Deferred Income Tax Expense (Benefit)			296	14	$ 26
Net income (loss) attributable to parent			2,950	2,568	2,870
Income tax benefit			(598)	(583)	(554)
Equity income (loss)			(44)	43	(151)
Reclassification of long-term income tax receivable				(609)
Long-term income tax receivable adjustments			(40)	17
Related Party Transaction, Cash Received for Income Taxes, Net			900	900	$ 636
Deferred Income Tax Charge [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Regulatory Liabilities	[1]		3,611	$ 3,923
Tax Cuts and Jobs Act of 2017 [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Current Income Tax Expense (Benefit)			$ 68
Federal statutory income tax rate			21.00%	21.00%
Deferred Tax Liabilities, Net	[2]		$ 7,115
Deferred Income Tax Expense (Benefit)			68
Increase (decrease) in provisional tax liabilities				$ 134
Increase (Decrease) in Deferred Income Taxes			(27)
Tax Cuts and Jobs Act of 2017 [Member] | Deferred Income Tax Charge [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Regulatory Liabilities	[2]		5,950
Deferred Income Tax Expense (Benefit)	[2]	$ 1,150
Net income (loss) attributable to parent	[2]		516
Income tax benefit	[2]	1,150
Foreign Earnings Repatriated		419
Equity income (loss)		$ 228
Increase in Regulatory Liability			27
Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Deferred Tax Liabilities, Net			61
Deferred Income Tax Expense (Benefit)			2
Iowa Senate File 2417, Rate Effective Starting 2021 [Member] | Deferred Income Tax Charge [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Increase in Regulatory Liability			59
State and Local Jurisdiction [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Operating Loss Carryforwards	[3]		5,819
State and Local Jurisdiction [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Operating Loss Carryforwards			$ 79	53
Maximum [Member] | IOWA | Tax Year, Current [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Statutory Income Tax Rate, State and Local, Percent			12.00%
Maximum [Member] | IOWA | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Statutory Income Tax Rate, State and Local, Percent			9.80%
Long-term income tax receivable [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Reclassification of long-term income tax receivable			$ (609)
Long-term income tax receivable adjustments			(73)	$ 152
Long-term income tax receivable [Member] | Iowa Senate File 2417, Rate Effective Starting 2021 [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Reclassification of long-term income tax receivable			(609)
Long-term income tax receivable adjustments			115
Parent Company [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Related Party Transaction, Cash Received for Income Taxes, Net			$ 90

[1] (1)Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to certain property-related basis differences and other various differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse. See Note 12 for further discussion of 2017 Tax Reform impacts.

[2] Amounts primarily represent income tax liabilities related to the federal tax rate change from 35% to 21% that are probable to be passed on to customers, offset by income tax benefits related to accelerated tax depreciation and certain property-related basis differences that were previously passed on to customers and will be included in regulated rates when the temporary differences reverse.

[3] 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 2020.