Electric utility segment - Annual decoupling filings summary (Details)	Mar. 31, 2017 USD ($) kWh
Hawaiian Electric Company
Regulatory projects and legal obligations
2017 Annual incremental RAM adjusted revenues	$ 12,700,000
Annual change in accrued earnings sharing credits	0
Annual change in accrued RBA balance as of December 31, 2016 (and associated revenue taxes) (refunded)	(2,400,000)
Net annual incremental amount to be collected under the tariffs	10,300,000
Impact on typical residential customer monthly bill (in dollars)	$ 0.60
Monthly utility usage assumption (in kilowatt hours) | kWh	500
HELCO
Regulatory projects and legal obligations
2017 Annual incremental RAM adjusted revenues	$ 3,200,000
Annual change in accrued earnings sharing credits	0
Annual change in accrued RBA balance as of December 31, 2016 (and associated revenue taxes) (refunded)	(2,500,000)
Net annual incremental amount to be collected under the tariffs	700,000
Impact on typical residential customer monthly bill (in dollars)	$ 0.15
Monthly utility usage assumption (in kilowatt hours) | kWh	500
Maui Electric
Regulatory projects and legal obligations
2017 Annual incremental RAM adjusted revenues	$ 1,600,000
Annual change in accrued earnings sharing credits	0
Annual change in accrued RBA balance as of December 31, 2016 (and associated revenue taxes) (refunded)	(200,000)
Net annual incremental amount to be collected under the tariffs	1,400,000
Impact on typical residential customer monthly bill (in dollars)	$ 0.79
Monthly utility usage assumption (in kilowatt hours) | kWh	500
Lanai and Molokai
Regulatory projects and legal obligations
Impact on typical residential customer monthly bill (in dollars)	$ 0.63
Monthly utility usage assumption (in kilowatt hours) | kWh	400