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, 2019 USD ($)	Dec. 31, 2018 USD ($)
Prepayment rate:
25 basis points adverse rate change	$ (950)	$ (250)
50 basis points adverse rate change	(1,947)	(566)
Discount rate:
25 basis points adverse rate change	(102)	(139)
50 basis points adverse rate change	(202)	(275)
American Savings Bank (ASB)
Mortgage Servicing Rights
Unpaid principal balance	$ 1,276,437	$ 1,188,514
Weighted average note rate	3.96%	3.98%
American Savings Bank (ASB) | Discount rate
Mortgage Servicing Rights
Weighted average measurement input	0.093	0.100
American Savings Bank (ASB) | Prepayment speed
Mortgage Servicing Rights
Weighted average measurement input	0.114	0.065