Bank segment - Mortgage servicing rights (Details) - American Savings Bank (ASB) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)
Servicing Asset at Amortized Cost [Line Items]
Repurchase reserve			$ 100		$ 100
Mortgage service fees	$ 700	$ 700
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Servicing asset - beginning balance	8,062
Servicing asset - ending balance	7,897
Residential loan
Servicing Asset at Amortized Cost [Line Items]
Proceeds from sale of mortgage loans	24,900	33,100
Gain on sale of mortgage loans	600	600
Servicing contracts
Servicing Asset at Amortized Cost [Line Items]
Gross carrying amount			18,786	$ 18,556
Accumulated amortization			(10,889)	(10,494)
Valuation allowance	0	0	0	0	0
Net carrying amount			7,897	8,062	$ 8,541
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Servicing asset - beginning balance	8,062	8,639
Amount capitalized	230	335
Amortization	(395)	(433)
Other-than-temporary impairment	0	0
Servicing asset - ending balance	7,897	8,541
Valuation Allowance [Roll Forward]
Valuation allowance, beginning balance	0	0
Provision (recovery)	0	0
Other-than-temporary impairment	0	0
Valuation allowance, ending balance	$ 0	$ 0
Unpaid principal balance			1,172,573	1,188,514
Prepayment rate:
25 basis points adverse rate change			(421)	(250)
50 basis points adverse rate change			(962)	(566)
Discount rate:
25 basis points adverse rate change			(126)	(139)
50 basis points adverse rate change			$ (251)	$ (275)
Servicing contracts | Note rate
Valuation Allowance [Roll Forward]
Weighted average measurement input			0.0399	0.0398
Servicing contracts | Discount rate
Valuation Allowance [Roll Forward]
Weighted average measurement input			0.100	0.100
Servicing contracts | Prepayment speed
Valuation Allowance [Roll Forward]
Weighted average measurement input			0.074	0.065
Measurement Band A
Valuation Allowance [Roll Forward]
Measurement band percent for risk categorization	0.50%
Measurement Band B
Valuation Allowance [Roll Forward]
Measurement band percent for risk categorization	1.00%