Bank segment (HEI only) - Securities Sold Under Agreements to Repurchase, Including Related Collateral Received From or Pledged to Counterparties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Securities sold under agreements to repurchase
Gross amount of recognized liabilities	$ 90,000	$ 115,000
Gross amount  offset in the  Balance Sheets	0	0
Net amount of  liabilities presented in the Balance Sheets	$ 90,000	115,000
Fair value of collateral, percent of fair value	5.00%
Repurchase liability	$ 89,670	$ 115,110
Weighted-average interest rate as of end of the period	0.02%	0.98%
Identical securities
Securities sold under agreements to repurchase
Repurchase liability	$ 89,670	$ 115,110	$ 65,040
Average amount outstanding during the year	73,738	79,598	99,162
Maximum amount outstanding as of any month-end	$ 100,580	$ 115,110	$ 152,255
Weighted-average interest rate as of end of the period	0.02%	0.98%	0.75%
Weighted-average interest rate during the year	0.42%	0.96%	0.71%
Weighted-average remaining days to maturity as of end of the period	1 day	1 day	1 day
Commercial account holders
Securities sold under agreements to repurchase
Net amount of  liabilities presented in the Balance Sheets	$ 90,000	$ 115,000
Financial instruments	92,000	130,000
Cash collateral pledged	$ 0	$ 0