Electric utility segment - Condensed consolidating statement of income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Income Statements, Captions [Line Items]
Revenues	$ 591,562	$ 550,960
Expenses
Purchased power	127,000	116,000
Total expenses	523,700	482,109
Total operating income	67,862	68,851
Allowance for equity funds used during construction	2,399	1,739
Allowance for borrowed funds used during construction	889	662
Income taxes	16,916	18,301
Net income	34,666	32,825
Preferred stock dividends of subsidiaries	473	473
Net income for common stock	34,193	32,352
Hawaiian Electric Company
Condensed Income Statements, Captions [Line Items]
Revenues	362,843	337,175
Expenses
Fuel oil	98,001	74,085
Purchased power	100,147	91,917
Other operation and maintenance	67,278	69,558
Depreciation	32,722	31,522
Taxes, other than income taxes	35,040	32,684
Total expenses	333,188	299,766
Total operating income	29,655	37,409
Allowance for equity funds used during construction	2,056	1,406
Equity in earnings of subsidiaries	8,603	7,929
Interest expense and other charges, net	(12,057)	(11,865)
Allowance for borrowed funds used during construction	749	529
Income before income taxes	29,006	35,408
Income taxes	7,271	9,771
Net income	21,735	25,637
Preferred stock dividends of subsidiaries	0	0
Net income attributable to Hawaiian Electric	21,735	25,637
Preferred stock dividends of Hawaiian Electric	270	270
Net income for common stock	21,465	25,367
HELCO
Condensed Income Statements, Captions [Line Items]
Revenues	78,982	73,183
Expenses
Fuel oil	17,257	14,374
Purchased power	18,589	16,797
Other operation and maintenance	15,516	16,441
Depreciation	9,685	9,449
Taxes, other than income taxes	7,450	6,891
Total expenses	68,497	63,952
Total operating income	10,485	9,231
Allowance for equity funds used during construction	115	127
Equity in earnings of subsidiaries	0	0
Interest expense and other charges, net	(3,004)	(2,965)
Allowance for borrowed funds used during construction	45	49
Income before income taxes	7,641	6,442
Income taxes	2,923	2,346
Net income	4,718	4,096
Preferred stock dividends of subsidiaries	134	134
Net income attributable to Hawaiian Electric	4,584	3,962
Preferred stock dividends of Hawaiian Electric	0	0
Net income for common stock	4,584	3,962
Maui Electric
Condensed Income Statements, Captions [Line Items]
Revenues	76,793	71,706
Expenses
Fuel oil	29,012	25,281
Purchased power	8,388	7,145
Other operation and maintenance	17,446	17,909
Depreciation	5,809	5,810
Taxes, other than income taxes	7,333	6,863
Total expenses	67,988	63,008
Total operating income	8,805	8,698
Allowance for equity funds used during construction	228	206
Equity in earnings of subsidiaries	0	0
Interest expense and other charges, net	(2,450)	(2,490)
Allowance for borrowed funds used during construction	95	84
Income before income taxes	6,678	6,498
Income taxes	2,564	2,436
Net income	4,114	4,062
Preferred stock dividends of subsidiaries	95	95
Net income attributable to Hawaiian Electric	4,019	3,967
Preferred stock dividends of Hawaiian Electric	0	0
Net income for common stock	4,019	3,967
Other subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	0	0
Expenses
Fuel oil	0	0
Purchased power	0	0
Other operation and maintenance	0	0
Depreciation	0	0
Taxes, other than income taxes	0	0
Total expenses	0	0
Total operating income	0	0
Allowance for equity funds used during construction	0	0
Equity in earnings of subsidiaries	0	0
Interest expense and other charges, net	0	0
Allowance for borrowed funds used during construction	0	0
Income before income taxes	0	0
Income taxes	0	0
Net income	0	0
Preferred stock dividends of subsidiaries	0	0
Net income attributable to Hawaiian Electric	0	0
Preferred stock dividends of Hawaiian Electric	0	0
Net income for common stock	0	0
Consolidating adjustments
Condensed Income Statements, Captions [Line Items]
Revenues	(7)	(12)
Expenses
Fuel oil	0	0
Purchased power	0	0
Other operation and maintenance	0	0
Depreciation	0	0
Taxes, other than income taxes	0	0
Total expenses	0	0
Total operating income	(7)	(12)
Allowance for equity funds used during construction	0	0
Equity in earnings of subsidiaries	(8,603)	(7,929)
Interest expense and other charges, net	7	12
Allowance for borrowed funds used during construction	0	0
Income before income taxes	(8,603)	(7,929)
Income taxes	0	0
Net income	(8,603)	(7,929)
Preferred stock dividends of subsidiaries	0	0
Net income attributable to Hawaiian Electric	(8,603)	(7,929)
Preferred stock dividends of Hawaiian Electric	0	0
Net income for common stock	(8,603)	(7,929)
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenues	518,611	482,052
Expenses
Fuel oil	144,270	113,740
Purchased power	127,124	115,859
Other operation and maintenance	100,240	103,908
Depreciation	48,216	46,781
Taxes, other than income taxes	49,823	46,438
Total expenses	469,673	426,726
Total operating income	48,938	55,326
Allowance for equity funds used during construction	2,399	1,739
Equity in earnings of subsidiaries	0	0
Interest expense and other charges, net	(17,504)	(17,308)
Allowance for borrowed funds used during construction	889	662
Income before income taxes	34,722	40,419
Income taxes	12,758	14,553
Net income	21,964	25,866
Preferred stock dividends of subsidiaries	229	229
Net income attributable to Hawaiian Electric	21,735	25,637
Preferred stock dividends of Hawaiian Electric	270	270
Net income for common stock	$ 21,465	$ 25,367