Consolidated Statements of Comprehensive Income - HECO - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income for common stock	$ 49,573	$ 65,900	$ 46,054	$ 40,247	$ 32,370	$ 60,073	$ 38,661	$ 34,193	$ 201,774	$ 165,297	$ 248,256
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, nil and $179 for 2018, 2017 and 2016, respectively									0	0	(281)
Reclassification adjustment to net income, net of (taxes) benefits of nil, $289 and $(110) for 2018, 2017 and 2016, respectively									0	454	(119)
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits of $9,024, $(39,587) and $27,153 for 2018, 2017 and 2016, respectively									(28,101)	65,531	(43,510)
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $6,594, $9,221 and $8,442 for 2018, 2017 and 2016, respectively									21,015	15,737	14,518
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(2,887), $49,523 and $(18,206) for 2018, 2017 and 2016, respectively									8,325	(78,724)	28,584
Other comprehensive income (loss), net of taxes									(8,669)	(1,372)	(6,867)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									193,105	163,925	241,389
Hawaiian Electric Company, Inc. and Subsidiaries
Net income for common stock	$ 35,297	$ 49,712	$ 31,169	$ 27,475	$ 25,355	$ 47,487	$ 25,644	$ 21,465	143,653	119,951	142,317
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, nil and $179 for 2018, 2017 and 2016, respectively									0	0	(281)
Reclassification adjustment to net income, net of (taxes) benefits of nil, $289 and $(110) for 2018, 2017 and 2016, respectively									0	454	(173)
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits of $9,024, $(39,587) and $27,153 for 2018, 2017 and 2016, respectively									(26,019)	63,105	(42,631)
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $6,594, $9,221 and $8,442 for 2018, 2017 and 2016, respectively									19,012	14,477	13,254
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(2,887), $49,523 and $(18,206) for 2018, 2017 and 2016, respectively									8,325	(78,724)	28,584
Other comprehensive income (loss), net of taxes									1,318	(688)	(1,247)
Comprehensive income attributable to Hawaiian Electric Company, Inc.									$ 144,971	$ 119,263	$ 141,070