Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flows from operating activities
Net cash provided by operating activities	$ 61,293	$ 77,169
Cash flows from investing activities
Capital expenditures	(125,554)	(120,424)
Other	2,942	3,932
Net cash used in investing activities	(260,463)	(82,978)
Cash flows from financing activities
Common stock dividends	(36,018)	(34,860)
Proceeds from issuance of short-term debt	(135,710)	11,407
Proceeds from issuance of long-term debt	186,925	550
Repayment of long-term debt	(909)	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	42,495	(20,170)
Other	(4,590)	(4,257)
Net cash provided by financing activities	207,901	23,008
Net increase in cash, cash equivalents and restricted cash	8,731	17,199
Cash, cash equivalents and restricted cash, beginning of period	227,685	169,208
Cash, cash equivalents and restricted cash, end of period	236,416	186,407
Less: Restricted cash	(30,902)	0	$ (30,872)
Cash and cash equivalents, end of period	205,514	186,407	196,813
Consolidating adjustments
Cash flows from operating activities
Net cash provided by operating activities	(7,272)	(6,311)
Cash flows from investing activities
Capital expenditures	0	0
Advances from (to) affiliates	9,000	18,700
Other	(404)	0
Net cash used in investing activities	8,596	18,700
Cash flows from financing activities
Common stock dividends	7,676	6,311
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(9,000)	(18,700)
Other	0	0
Net cash provided by financing activities	(1,324)	(12,389)
Net increase in cash, cash equivalents and restricted cash	0	0
Cash, cash equivalents and restricted cash, beginning of period	0	0
Cash, cash equivalents and restricted cash, end of period	0	0
Less: Restricted cash	0		0
Cash and cash equivalents, end of period	0		0
Hawaiian Electric (parent only) | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	29,004	58,145
Cash flows from investing activities
Capital expenditures	(83,191)	(78,220)
Advances from (to) affiliates	(17,000)	(9,500)
Other	2,752	1,221
Net cash used in investing activities	(97,439)	(86,499)
Cash flows from financing activities
Common stock dividends	(26,784)	(25,313)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(270)	(270)
Proceeds from issuance of short-term debt	50,000	25,000
Proceeds from issuance of long-term debt	95,000
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(46,987)	15,199
Other	(21)	0
Net cash provided by financing activities	70,938	14,616
Net increase in cash, cash equivalents and restricted cash	2,503	(13,738)
Cash, cash equivalents and restricted cash, beginning of period	32,988	16,732
Cash, cash equivalents and restricted cash, end of period	35,491	2,994
Less: Restricted cash	(30,902)		(30,749)
Cash and cash equivalents, end of period	4,589		2,239
HELCO | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	9,478	8,745
Cash flows from investing activities
Capital expenditures	(18,181)	(8,371)
Advances from (to) affiliates	8,000	(9,200)
Other	64	(293)
Net cash used in investing activities	(10,117)	(17,864)
Cash flows from financing activities
Common stock dividends	(4,080)	(2,544)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(134)	(134)
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	2,500	0
Other	(1)	(1)
Net cash provided by financing activities	(1,715)	(2,679)
Net increase in cash, cash equivalents and restricted cash	(2,354)	(11,798)
Cash, cash equivalents and restricted cash, beginning of period	7,008	15,623
Cash, cash equivalents and restricted cash, end of period	4,654	3,825
Less: Restricted cash	0		(123)
Cash and cash equivalents, end of period	4,654		6,885
Maui Electric | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	7,931	8,837
Cash flows from investing activities
Capital expenditures	(17,772)	(16,300)
Advances from (to) affiliates	0	0
Other	301	(134)
Net cash used in investing activities	(17,471)	(16,434)
Cash flows from financing activities
Common stock dividends	(3,596)	(3,767)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(95)	(95)
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	14,500	9,500
Other	(1)	(1)
Net cash provided by financing activities	10,808	5,637
Net increase in cash, cash equivalents and restricted cash	1,268	(1,960)
Cash, cash equivalents and restricted cash, beginning of period	1,797	3,421
Cash, cash equivalents and restricted cash, end of period	3,065	1,461
Less: Restricted cash	0		0
Cash and cash equivalents, end of period	3,065		1,797
Other subsidiaries | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	0	0
Cash flows from investing activities
Capital expenditures	0	0
Advances from (to) affiliates	0	0
Other	0	0
Net cash used in investing activities	0	0
Cash flows from financing activities
Common stock dividends	0	0
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	0	0
Other	0	0
Net cash provided by financing activities	0	0
Net increase in cash, cash equivalents and restricted cash	0	0
Cash, cash equivalents and restricted cash, beginning of period	101	101
Cash, cash equivalents and restricted cash, end of period	101	101
Less: Restricted cash	0		0
Cash and cash equivalents, end of period	101		101
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net cash provided by operating activities	39,141	69,416
Cash flows from investing activities
Capital expenditures	(119,144)	(102,891)
Advances from (to) affiliates	0	0
Other	2,713	794
Net cash used in investing activities	(116,431)	(102,097)
Cash flows from financing activities
Common stock dividends	(26,784)	(25,313)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(499)	(499)
Proceeds from issuance of short-term debt	50,000	25,000
Proceeds from issuance of long-term debt	95,000	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(38,987)	5,999
Other	(23)	(2)
Net cash provided by financing activities	78,707	5,185
Net increase in cash, cash equivalents and restricted cash	1,417	(27,496)
Cash, cash equivalents and restricted cash, beginning of period	41,894	35,877
Cash, cash equivalents and restricted cash, end of period	43,311	8,381
Less: Restricted cash	(30,902)	0	(30,872)
Cash and cash equivalents, end of period	$ 12,409	$ 8,381	$ 11,022