Notes payable and other borrowings - Credit agreements - Narrative (Detail) - Line of Credit and Commercial Paper Facilities [Member] - Subsidiaries [Member] $ in Billions	Sep. 30, 2019 USD ($)
Line of Credit Facility [Line Items]
Unused lines of credit available	$ 7.2
Berkshire Hathaway Energy and Subsidiaries [Member]
Line of Credit Facility [Line Items]
Unused lines of credit available	$ 5.7

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant