Retirement benefits (Details) - HECO (USD $)	6 Months Ended		12 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Maximum	Jun. 30, 2013 Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2013 Pension benefits	Jun. 30, 2012 Pension benefits	Jun. 30, 2013 Pension benefits	Jun. 30, 2012 Pension benefits	Jun. 30, 2013 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2012 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2013 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2012 Pension benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2013 Other benefits	Jun. 30, 2012 Other benefits	Jun. 30, 2013 Other benefits	Jun. 30, 2012 Other benefits	Jun. 30, 2013 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2012 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2013 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries	Jun. 30, 2012 Other benefits Hawaiian Electric Company, Inc. and Subsidiaries
Retirement benefits
Contributions made to defined benefit plans					$ 41,000,000	$ 52,000,000
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
Funded status of retirement plan (as a percent)				80.00%
Defined benefit plans
Service cost								14,121,000	11,397,000	28,210,000	21,588,000	13,638,000	11,000,000	27,241,000	20,802,000	1,103,000	1,008,000	2,152,000	2,104,000	1,067,000	959,000	2,081,000	2,007,000
Interest cost								16,307,000	16,973,000	32,413,000	33,744,000	14,883,000	15,465,000	29,559,000	30,726,000	1,855,000	2,223,000	3,786,000	4,504,000	1,783,000	2,147,000	3,644,000	4,352,000
Expected return on plan assets								(18,182,000)	(17,736,000)	(36,267,000)	(35,592,000)	(16,185,000)	(15,942,000)	(32,275,000)	(32,002,000)	(2,521,000)	(2,557,000)	(5,083,000)	(5,178,000)	(2,480,000)	(2,519,000)	(5,000,000)	(5,098,000)
Amortization of net transition obligation																					(2,000)		(4,000)
Amortization of net prior service gain								(25,000)	(82,000)	(49,000)	(163,000)	(116,000)	(172,000)	(232,000)	(344,000)	(449,000)	(449,000)	(897,000)	(897,000)	(451,000)	(451,000)	(902,000)	(902,000)
Amortization of net actuarial loss								9,499,000	6,403,000	19,318,000	12,826,000	8,509,000	5,845,000	17,299,000	11,714,000	284,000	299,000	805,000	752,000	268,000	288,000	772,000	728,000
Net periodic benefit cost								21,720,000	16,955,000	43,625,000	32,403,000	20,729,000	16,196,000	41,592,000	30,896,000	272,000	524,000	763,000	1,285,000	187,000	422,000	595,000	1,083,000
Impact of PUC D&Os								(5,286,000)	(4,977,000)	(12,722,000)	(8,834,000)	(5,286,000)	(4,977,000)	(12,722,000)	(8,834,000)	(187,000)	(416,000)	(584,000)	(1,096,000)	(187,000)	(416,000)	(584,000)	(1,096,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)								16,434,000	11,978,000	30,903,000	23,569,000	15,443,000	11,219,000	28,870,000	22,062,000	85,000	108,000	179,000	189,000		6,000	11,000	(13,000)
Retirement benefits expense	23,000,000	17,000,000			21,000,000	15,000,000
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	$ 2,000,000	$ 1,800,000			$ 300,000	$ 300,000