Retirement benefits (Details) - HECO (USD $)	9 Months Ended		12 Months Ended	9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2013 Pension benefits	Sep. 30, 2012 Pension benefits	Sep. 30, 2013 Pension benefits	Sep. 30, 2012 Pension benefits	Sep. 30, 2013 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2013 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2013 Other benefits	Sep. 30, 2012 Other benefits	Sep. 30, 2013 Other benefits	Sep. 30, 2012 Other benefits	Sep. 30, 2013 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2013 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries
Retirement benefits
Contributions made to defined benefit plans				$ 61,000,000	$ 62,000,000
Current estimate of contributions to defined benefit plans in current fiscal year	83,000,000		78,000,000	81,000,000		63,000,000
Benefits expected to be paid directly by the company in current fiscal year, comparable to prior year	2,000,000		1,000,000	1,000,000		500,000
Defined benefit plans
Service cost							14,097,000	10,816,000	42,307,000	32,404,000	13,620,000	10,400,000	40,861,000	31,202,000	1,077,000	1,054,000	3,229,000	3,158,000	1,041,000	1,003,000	3,122,000	3,010,000
Interest cost							16,187,000	16,868,000	48,600,000	50,612,000	14,780,000	15,364,000	44,339,000	46,090,000	1,891,000	2,252,000	5,677,000	6,756,000	1,822,000	2,175,000	5,466,000	6,527,000
Expected return on plan assets							(18,134,000)	(17,796,000)	(54,401,000)	(53,388,000)	(16,138,000)	(16,001,000)	(48,413,000)	(48,003,000)	(2,531,000)	(2,579,000)	(7,614,000)	(7,757,000)	(2,502,000)	(2,548,000)	(7,502,000)	(7,646,000)
Amortization of net transition obligation																				(2,000)		(6,000)
Amortization of net prior service gain							(24,000)	(81,000)	(73,000)	(244,000)	(116,000)	(173,000)	(348,000)	(517,000)	(448,000)	(448,000)	(1,345,000)	(1,345,000)	(451,000)	(450,000)	(1,353,000)	(1,352,000)
Amortization of net actuarial loss							9,560,000	6,425,000	28,878,000	19,251,000	8,649,000	5,857,000	25,948,000	17,571,000	398,000	373,000	1,203,000	1,125,000	387,000	363,000	1,159,000	1,091,000
Net periodic benefit cost							21,686,000	16,233,000	65,311,000	48,636,000	20,795,000	15,447,000	62,387,000	46,343,000	387,000	652,000	1,150,000	1,937,000	297,000	541,000	892,000	1,624,000
Impact of PUC D&Os							(9,257,000)	(3,460,000)	(28,847,000)	(12,294,000)	(9,257,000)	(3,460,000)	(28,847,000)	(12,294,000)	(332,000)	(552,000)	(1,018,000)	(1,648,000)	(332,000)	(552,000)	(1,018,000)	(1,648,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)							12,429,000	12,773,000	36,464,000	36,342,000	11,538,000	11,987,000	33,540,000	34,049,000	55,000	100,000	132,000	289,000	(35,000)	(11,000)	(126,000)	(24,000)
Retirement benefits expense	24,000,000	27,000,000		21,000,000	24,000,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case	5 years			5 years
Defined contribution plan, expenses recognized	$ 3,100,000	$ 2,700,000		$ 400,000	$ 200,000