Consolidated Statements of Comprehensive Income - HECO - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income for common stock	$ 32,370	$ 60,073	$ 38,661	$ 34,193	$ 44,634	$ 127,142	$ 44,128	$ 32,352	$ 165,297	$ 248,256	$ 159,877
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 nil, $179 and nil for 2017, 2016 and 2015, respectively									0	(281)	0
Reclassification adjustment to net income, net of taxes of $289, $110 and nil for 2017, 2016 and 2015, respectively									454	(119)	235
Retirement benefit plans:
Net gains arising during the period, net of taxes of nil, nil and $59 for 2017, 2016 and 2015, respectively									65,531	(43,510)	5,889
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $812, $566 and $1,011 for 2017, 2016 and 2015, respectively									15,737	14,518	22,465
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $49,523, $(18,206) and $16,011 for 2017, 2016 and 2015, respectively									(78,724)	28,584	(25,139)
Other comprehensive income (loss), net of taxes									(1,372)	(6,867)	1,116
Comprehensive income attributable to Hawaiian Electric Company, Inc.									163,925	241,389	160,993
Hawaiian Electric Company, Inc. and Subsidiaries
Net income for common stock	$ 25,355	$ 47,487	$ 25,644	$ 21,465	$ 34,119	$ 46,974	$ 35,857	$ 25,367	119,951	142,317	135,714
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 nil, $179 and nil for 2017, 2016 and 2015, respectively									0	(281)	0
Reclassification adjustment to net income, net of taxes of $289, $110 and nil for 2017, 2016 and 2015, respectively									454	(173)	0
Retirement benefit plans:
Net gains arising during the period, net of taxes of nil, nil and $59 for 2017, 2016 and 2015, respectively									63,105	(42,631)	5,638
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $812, $566 and $1,011 for 2017, 2016 and 2015, respectively									14,477	13,254	20,381
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $49,523, $(18,206) and $16,011 for 2017, 2016 and 2015, respectively									(78,724)	28,584	(25,139)
Other comprehensive income (loss), net of taxes									(688)	(1,247)	880
Comprehensive income attributable to Hawaiian Electric Company, Inc.									$ 119,263	$ 141,070	$ 136,594