Income Taxes Income Tax Examination (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Examination [Line Items]
Increases (decreases) for interest and penalties	$ 7	$ 6
Income Tax Examination, Description	All U.S. federal income tax returns of BNSF are closed for audit through the tax period ended December 31, 2011. BNSF is currently under examination for the years 2012 and 2013 through Berkshire's consolidated U.S. federal income tax return.

A brief description of status of the tax examination, significant findings to date, and the entity's position with respect to the findings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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