Bank segment (HEI only) - Key Assumptions Used in Estimating the Fair Value of ASB's Mortgage Servicing Rights (Details) - Allowance for mortgage-servicing assets – bank $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Prepayment rate:
25 basis points adverse rate change	$ (738)	$ (950)
50 basis points adverse rate change	(1,445)	(1,947)
Discount rate:
25 basis points adverse rate change	(68)	(102)
50 basis points adverse rate change	(135)	(202)
American Savings Bank (ASB)
Mortgage Servicing Rights
Unpaid principal balance	$ 1,450,312	$ 1,276,437
Weighted average note rate	3.68%	3.96%
American Savings Bank (ASB) | Discount rate
Mortgage Servicing Rights
Weighted average measurement input	0.0925	0.0925
American Savings Bank (ASB) | Prepayment speed
Mortgage Servicing Rights
Weighted average measurement input	0.177	0.114