Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income for common stock	$ 201,774	$ 165,297	$ 248,256
Net unrealized losses on available-for sale investment securities:
Net unrealized losses on available-for sale investment securities arising during the period, net of tax benefits of $3,468, $2,886 and $3,763 for 2018, 2017 and 2016, respectively	(9,472)	(4,370)	(5,699)
Reclassification adjustment for net realized gains included in net income, net of taxes of nil, nil and $238 for 2018, 2017 and 2016, respectively	0	0	(360)
Derivatives qualified as cash flow hedges:
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)
Unrealized interest rate hedging gain (loss), net of tax (expense) benefit of $151, nil and nil for 2018, 2017 and 2016, respectively	(436)	0	0
Reclassification adjustment to net income, net of (taxes) benefits of nil, $289 and $(76) for 2018, 2017 and 2016, respectively	0	454	(119)
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits of $9,810, $(41,129) and $27,703 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 $7,317, $10,041 and $9,267 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