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, 2018	Dec. 31, 2017	Dec. 31, 2016
Securities sold under agreements to repurchase
Gross amount of recognized liabilities	$ 65,000	$ 141,000
Gross amount offset in the Balance Sheets	0	0
Net amount of liabilities presented in the Balance Sheets	$ 65,000	141,000
Fair value of collateral, percent of fair value	5.00%
Repurchase liability	$ 65,040	$ 140,859
Weighted-average interest rate as of end of the period	0.75%	0.65%
Identical securities
Securities sold under agreements to repurchase
Repurchase liability	$ 65,000	$ 141,000	$ 93,000
Average amount outstanding during the year	99,000	98,000	170,000
Maximum amount outstanding as of any month-end	$ 152,000	$ 141,000	$ 229,000
Weighted-average interest rate as of end of the period	0.75%	0.65%	0.23%
Weighted-average interest rate during the year	0.71%	0.26%	1.43%
Weighted-average remaining days to maturity as of end of the period	1 day	1 day	6 days
Commercial account holders
Securities sold under agreements to repurchase
Net amount of liabilities presented in the Balance Sheets	$ 65,000	$ 141,000
Financial instruments	92,000	165,000
Cash collateral pledged	$ 0	$ 0