Consolidating financial information (Details 4) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended											3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 HECO	Mar. 31, 2012 HECO	Mar. 31, 2013 HELCO	Mar. 31, 2012 HELCO	Mar. 31, 2013 MECO	Mar. 31, 2012 MECO	Mar. 31, 2012 Other subsidiaries	Mar. 31, 2013 Other subsidiaries	Dec. 31, 2012 Other subsidiaries	Mar. 31, 2013 Consolidating adjustments	Mar. 31, 2012 Consolidating adjustments	Mar. 31, 2013 HECO Consolidated	Mar. 31, 2012 HECO Consolidated
Balance	$ 1,593,865	$ 1,528,706	$ 1,472,136	$ 1,402,841	$ 268,908	$ 280,468	$ 228,927	$ 235,568	$ 107	$ 104	$ 104	$ (497,939)	$ (516,143)	$ 1,472,136	$ 1,402,841
Net income (loss) for common stock	33,679	38,316	24,429	27,300	4,420	6,611	6,565	1,880	(1)			(10,985)	(8,490)	24,429	27,300
Other comprehensive income (loss)	(61)	311	18	77	(2)	6	1	6				1	(12)	18	77
Common stock dividends	(30,434)	(29,817)	(20,070)	(18,261)	(3,610)	(3,284)	(3,442)	(2,187)				7,052	5,471	(20,070)	(18,261)
Balance	$ 1,607,265	$ 1,550,855	$ 1,476,513	$ 1,411,957	$ 269,716	$ 283,801	$ 232,051	$ 235,267	$ 106	$ 104	$ 104	$ (501,871)	$ (519,174)	$ 1,476,513	$ 1,411,957