Electric utility segment - Consolidating Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income for common stock	$ 44,634	$ 127,142	$ 44,128	$ 32,352	$ 42,320	$ 50,673	$ 35,018	$ 31,866	$ 248,256	$ 159,877	$ 168,129
Other comprehensive income (loss), net of taxes:
Effective portion of foreign currency hedge net unrealized losses arising during the period, net of tax benefits of $179, nil and nil for 2016, 2015 and 2014, respectively									(281)	0	0
Less: reclassification adjustment to net income, net of (taxes) benefit of $(76), $150 and $150 for 2016, 2015 and 2014, respectively									(119)	235	236
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									(43,510)	5,889	(234,166)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									14,518	22,465	11,344
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									28,584	(25,139)	207,833
Other comprehensive income (loss), net of taxes									(6,867)	1,116	(10,628)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									241,389	160,993	157,501
HECO
Net income for common stock									142,317	135,714	137,641
Other comprehensive income (loss), net of taxes:
Effective portion of foreign currency hedge net unrealized losses arising during the period, net of tax benefits of $179, nil and nil for 2016, 2015 and 2014, respectively									(281)
Less: reclassification adjustment to net income, net of (taxes) benefit of $(76), $150 and $150 for 2016, 2015 and 2014, respectively									(173)
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									(42,631)	5,638	(218,608)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									13,254	20,381	10,212
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									28,584	(25,139)	207,833
Other comprehensive income (loss), net of taxes									(1,247)	880	(563)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									141,070	136,594	137,078
Hawaii Electric Light Company, Inc. (HELCO)
Net income for common stock									21,255	20,755	18,689
Other comprehensive income (loss), net of taxes:
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									(5,141)	(2,710)	(28,725)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									1,718	2,728	1,270
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									3,269	104	27,437
Other comprehensive income (loss), net of taxes									(154)	122	(18)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									21,101	20,877	18,671
MECO
Net income for common stock									21,136	22,165	22,275
Other comprehensive income (loss), net of taxes:
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									(5,447)	(1,352)	(29,352)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									1,549	2,503	1,090
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									3,852	(1,107)	28,257
Other comprehensive income (loss), net of taxes									(46)	44	(5)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									21,090	22,209	22,270
Other subsidiaries
Net income for common stock									0	0	0
Other comprehensive income (loss), net of taxes:
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively											0
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively											0
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively											0
Other comprehensive income (loss), net of taxes											0
Comprehensive income attributable to Hawaiian Electric Company, Inc.									0	0	0
Consolidating adjustments
Net income for common stock									(42,391)	(42,920)	(40,964)
Other comprehensive income (loss), net of taxes:
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									10,588	4,062	58,077
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									(3,267)	(5,231)	(2,360)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									(7,121)	1,003	(55,694)
Other comprehensive income (loss), net of taxes									200	(166)	23
Comprehensive income attributable to Hawaiian Electric Company, Inc.									(42,191)	(43,086)	(40,941)
HECO Consolidated
Net income for common stock	$ 34,119	$ 46,974	$ 35,857	$ 25,367	$ 32,993	$ 43,006	$ 32,841	$ 26,874	142,317	135,714	137,641
Other comprehensive income (loss), net of taxes:
Effective portion of foreign currency hedge net unrealized losses arising during the period, net of tax benefits of $179, nil and nil for 2016, 2015 and 2014, respectively									(281)	0	0
Less: reclassification adjustment to net income, net of (taxes) benefit of $(76), $150 and $150 for 2016, 2015 and 2014, respectively									(173)	0	0
Net gains (losses) arising during the period, net of (taxes) benefits of $27,703, $(3,753) and $149,364 for 2016, 2015 and 2014, respectively									(42,631)	5,638	(218,608)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $9,267, $14,344 and $7,245 for 2016, 2015 and 2014, respectively									13,254	20,381	10,212
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(18,206), $16,011 and $(132,373) for 2016, 2015 and 2014, respectively									28,584	(25,139)	207,833
Other comprehensive income (loss), net of taxes									(1,247)	880	(563)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									$ 141,070	$ 136,594	$ 137,078