Cash flows (Details) - HECO (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Supplemental disclosures of cash flow information
Income taxes paid/(refunded)		$ (30)
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid	15	15
Income taxes paid/(refunded)	(1)	(33)
Supplemental disclosures of noncash activities
Electric utility property, plant and equipment - Unpaid invoices and other	$ 3	$ 1