Credit agreement (Details) - HECO	Mar. 31, 2014
Credit agreement
Ratio of consolidated subsidiary debt to total consolidated capitalization required to be maintained as per the debt covenant (as a percent)	65.00%
Ratio of consolidated capitalization required to be maintained as per the debt covenant (as a percent)	35.00%
Actual ratio of consolidated debt to total consolidated capitalization (as a percent)	56.00%
HELCO
Credit agreement
Actual ratio of consolidated subsidiary debt to total consolidated capitalization (as a percent)	42.00%
Maui Electric
Credit agreement
Actual ratio of consolidated subsidiary debt to total consolidated capitalization (as a percent)	45.00%