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, 2019	Dec. 31, 2018	Dec. 31, 2017
Securities sold under agreements to repurchase
Gross amount of recognized liabilities	$ 115,000	$ 65,000
Gross amount offset in the Balance Sheets	0	0
Net amount of liabilities presented in the Balance Sheets	$ 115,000	65,000
Fair value of collateral, percent of fair value	5.00%
Repurchase liability	$ 115,110	$ 65,040
Weighted-average interest rate as of end of the period	0.98%	0.75%
Identical securities
Securities sold under agreements to repurchase
Repurchase liability	$ 115,000	$ 65,000	$ 141,000
Average amount outstanding during the year	80,000	99,000	98,000
Maximum amount outstanding as of any month-end	$ 115,000	$ 152,000	$ 141,000
Weighted-average interest rate as of end of the period	0.98%	0.75%	0.65%
Weighted-average interest rate during the year	0.96%	0.71%	0.26%
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	$ 115,000	$ 65,000
Financial instruments	130,000	92,000
Cash collateral pledged	$ 0	$ 0