Share-based compensation (Details)	Sep. 30, 2013 Equity and Incentive Plan (EIP)	May 11, 2010 Stock Option and Incentive Plan (SOIP)	Sep. 30, 2013 Nonemployee Director Stock Plan (2011 Director Plan)
Share-based compensation
Shares remaining available for future issuance	3,600,000	0	202,460
Shares that can be issued upon vesting of outstanding units and achievement of performance goals	2,600,000

Represents the number of shares that could be issued upon vesting of share-based payment awards and achievement of performance goals.

No definition available.

Name:	he_ShareBasedCompensationNumberOfSharesThatCouldBeIssuedUponVestingAndAchievementOfPerformanceGoals
Namespace Prefix:	he_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant