Summary of significant accounting policies (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	$ 6,795	$ 4,667	[1]	$ 7,958	[1]
Increase (decrease) in deferred income taxes	103,916	80,399	[1]	90,848	[1]
Share-based compensation expense	9,287	7,780	[1]	6,698	[1]
Increase (decrease) in accounts, interest and dividends payable	(67,189)	12,406	[1]	5,497	[1]
Change in prepaid and accrued income taxes and utility revenue taxes	(39,091)	(19,406)	[1]	21,079	[1]
Change in other assets and liabilities	(94,966)	(11,696)	[1]	(102,275)	[1]
Net cash provided by operating activities	325,420	361,568	[1]	278,934	[1]
Capital expenditures	(364,826)	(389,438)	[1]	(370,715)	[1]
Cash flows from investing activities-Other	1,125	1,177	[1]	1,778	[1]
Net cash used in investing activities	(592,449)	(598,182)	[1]	(471,439)	[1]
Federal current taxes	(10,970)	(1,520)		(15,411)
Federal deferred taxes	91,159	73,680		82,138
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	43,000	(12,000)		(8,000)
Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	6,410	5,077	[1]	6,998	[1]
Increase (decrease) in accounts payable	(65,527)	14,731	[1]	6,322	[1]
Increase (decrease) in deferred income taxes	82,947	64,507	[1]	86,878	[1]
Change in prepaid and accrued income taxes and utility revenue taxes	(4,036)	(2,028)	[1]	25,239	[1]
Change in other assets and liabilities	(62,442)	(32,636)	[1]	(74,262)	[1]
Net cash provided by operating activities	306,995	326,865	[1]	221,623	[1]
Capital expenditures	(336,679)	(378,044)	[1]	(355,326)	[1]
Cash flows from investing activities-Other	1,164	907	[1]	843	[1]
Net cash used in investing activities	(293,709)	(344,977)	[1]	(308,501)	[1]
Federal current taxes	1,108	1,313		(26,965)
Federal deferred taxes	68,775	58,024		79,437
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	40,000	(12,000)		(8,000)
As previously filed
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	8,476
Increase (decrease) in deferred income taxes	59,184
Share-based compensation expense	0	0		0
Increase (decrease) in accounts, interest and dividends payable	(92,294)	(23,153)		(39,738)
Change in prepaid and accrued income taxes and utility revenue taxes	12,845
Change in other assets and liabilities	(93,400)	(2,779)		(94,734)
Net cash provided by operating activities	301,479	327,146		234,542
Capital expenditures	(339,721)	(353,879)		(325,480)
Cash flows from investing activities-Other	(39)	40		935
Net cash used in investing activities	(568,508)	(563,760)		(427,047)
Federal current taxes	33,762
Federal deferred taxes	46,427
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	68,000	24,000		37,000
As previously filed | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	8,091
Increase (decrease) in accounts payable	(90,632)	(20,828)		(38,913)
Change in other assets and liabilities	(62,959)	(31,499)		(73,419)
Net cash provided by operating activities	283,054	292,443		177,231
Capital expenditures	(311,574)	(342,485)		(310,091)
Cash flows from investing activities-Other	0	(230)		0
Net cash used in investing activities	(269,768)	(310,555)		(264,109)
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	65,000	24,000		37,000
Difference
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	(1,681)
Increase (decrease) in deferred income taxes	44,732
Share-based compensation expense	9,287	7,780		6,698
Increase (decrease) in accounts, interest and dividends payable	25,105	35,559		45,235
Change in prepaid and accrued income taxes and utility revenue taxes	(51,936)
Change in other assets and liabilities	(1,566)	(8,917)		(7,541)
Net cash provided by operating activities	23,941	34,422		44,392
Capital expenditures	(25,105)	(35,559)		(45,235)
Cash flows from investing activities-Other	1,164	1,137		843
Net cash used in investing activities	(23,941)	(34,422)		(44,392)
Federal current taxes	(44,732)
Federal deferred taxes	44,732
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	(25,000)	(36,000)		(45,000)
Difference | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other amortization	(1,681)
Increase (decrease) in accounts payable	25,105	35,559		45,235
Change in other assets and liabilities	517	(1,137)		(843)
Net cash provided by operating activities	23,941	34,422		44,392
Capital expenditures	(25,105)	(35,559)		(45,235)
Cash flows from investing activities-Other	1,164	1,137		843
Net cash used in investing activities	(23,941)	(34,422)		(44,392)
Additions to electric utility property, plant and equipment - unpaid invoices and other (investing)/______________________________ (in millions)	$ (25,000)	$ (36,000)		$ (45,000)

[1] As restated - See Note 1, “Summary of significant accounting policies - Revision and restatements of previously issued financial statements.”