Cash flows (Details) - HECO (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Supplemental disclosures of cash flow information
Income taxes paid/(refunded)	$ 1	$ 6
Supplemental disclosures of noncash activities
Additions to electric utility property, plant and equipment - Unpaid invoices and other	5	12
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid	30	29
Income taxes paid/(refunded)	(26)	3
Supplemental disclosures of noncash activities
Additions to electric utility property, plant and equipment - Unpaid invoices and other	$ 5	$ 12