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, 2018 USD ($)	Dec. 31, 2017 USD ($)
Prepayment rate:
25 basis points adverse rate change	$ (250)	$ (869)
50 basis points adverse rate change	(566)	(1,828)
Discount rate:
25 basis points adverse rate change	(139)	(111)
50 basis points adverse rate change	(275)	(220)
American Savings Bank (ASB)
Mortgage Servicing Rights
Unpaid principal balance	$ 1,188,514	$ 1,195,454
Weighted average note rate	3.98%	3.94%
American Savings Bank (ASB) | Discount rate
Mortgage Servicing Rights
Weighted average measurement input	0.100	0.100
American Savings Bank (ASB) | Prepayment speed
Mortgage Servicing Rights
Weighted average measurement input	0.065	0.090