Subsequent events (Details) - HECO (Hawaiian Electric Company, Inc. and Subsidiaries, USD $) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended
	Jul. 31, 2011 RAM	Jul. 22, 2011 RAM	Dec. 31, 2013	Jul. 22, 2011
Subsequent Events
Increase in annual revenues, net of RAM		$ 38.2
Increase in annual revenues, including RAM				$ 53.2
Percentage of increase in net of revenues (as a percent)	2.20%		3.10%