Basis of presentation (Details) - HECO (USD $) In Millions	9 Months Ended
	Sep. 30, 2011
Prior period adjustments
Decrease in operating cash flows related to unpaid invoices for electric utility property, plant and equipment	$ 13
Increase in investing cash flows related to unpaid invoices for electric utility property, plant and equipment	13
Hawaiian Electric Company, Inc. and Subsidiaries
Prior period adjustments
Decrease in operating cash flows related to unpaid invoices for electric utility property, plant and equipment	13
Increase in investing cash flows related to unpaid invoices for electric utility property, plant and equipment	$ 13