Share-based compensation LTIP Awards Linked To Other Performance Conditions (Details) (LTIP awards linked to other performance conditions, USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
LTIP awards linked to other performance conditions
Share-based Compensation, Long Term Incentive Plan [Roll Forward]
Outstanding, beginning of period (in shares)	296,843	247,175	182,498
Outstanding, beginning of period (in dollars per share)	$ 26.14	$ 25.04	$ 22.63
Granted (in shares)	129,603	120,399	125,157
Granted (in dollars per share)	$ 25.18	$ 26.89	$ 26.05
Vested (in shares)	(65,089)	(18,280)	0
Vested (in dollars per share)	$ 24.95	$ 18.95	$ 0.00
Increased above target (cancelled) (in shares)	4,949	(41,599)	(50,786)
Increased above target (cancelled) (in dollars per share)	$ 26.70	$ 24.97	$ 18.95
Forfeited (in shares)	(1,575)	(10,852)	(9,694)
Forfeited (in dollars per share)	$ 26.07	$ 26.20	$ 24.44
Outstanding, end of period (in shares)	364,731	296,843	247,175
Outstanding, end of period (in dollars per share)	$ 26.01	$ 26.14	$ 25.04
Total weighted-average grant-date fair value	$ 3.3	$ 3.2	$ 3.3

Share-based compensation LTIP Awards Linked To Other Performance Conditions (Details) (LTIP awards linked to other performance conditions, USD $)
In Millions, except Share data, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

LTIP awards linked to other performance conditions

Share-based Compensation, Long Term Incentive Plan [Roll Forward]

Outstanding, beginning of period (in shares)

296,843us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
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247,175us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
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182,498us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Outstanding, beginning of period (in dollars per share)

$ 26.14us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 25.04us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 22.63us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Granted (in shares)

129,603us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

120,399us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

125,157us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Granted (in dollars per share)

$ 25.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 26.89us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 26.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Vested (in shares)

(65,089)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

(18,280)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Vested (in dollars per share)

$ 24.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
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= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 18.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Increased above target (cancelled) (in shares)

4,949he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

(41,599)he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

(50,786)he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Increased above target (cancelled) (in dollars per share)

$ 26.70he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 24.97he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 18.95he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Forfeited (in shares)

(1,575)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

(10,852)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

(9,694)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Forfeited (in dollars per share)

$ 26.07he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionForfeitedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 26.20he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionForfeitedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 24.44he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionForfeitedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Outstanding, end of period (in shares)

364,731us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Outstanding, end of period (in dollars per share)

$ 26.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

Total weighted-average grant-date fair value

$ 3.3he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

$ 3.2he_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= he_LongTermIncentivePlanAwardsLinkedToOtherPerformanceConditionsMember

- Definition

Represents the weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan or when performance conditions met.

+ References

No definition available.

+ Details

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were cancelled during the reporting period.

+ References

No definition available.

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- Definition

The weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect during the reporting period as a result of the cancelled in during the period.

+ References

No definition available.

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- Definition

Represents the total weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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-Paragraph 2

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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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