Bank segment (HEI only) - Key Assumptions Used in Estimating the Fair Value of ASB's Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Mortgage Servicing Rights
Weighted average discount rate	3.048%
Allowance for mortgage-servicing assets – bank
Prepayment rate:
25 basis points adverse rate change	$ (869)	$ (567)
50 basis points adverse rate change	(1,828)	(1,154)
Discount rate:
25 basis points adverse rate change	(111)	(128)
50 basis points adverse rate change	(220)	(254)
Allowance for mortgage-servicing assets – bank | American Savings Bank (ASB)
Mortgage Servicing Rights
Unpaid principal balance	$ 1,195,454	$ 1,188,380
Weighted average note rate	3.94%	3.96%
Weighted average discount rate	10.00%	9.40%
Weighted average prepayment speed	9.00%	8.50%