Bank segment - Mortgage servicing rights (Details) - American Savings Bank (ASB) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)
Servicing Asset at Amortized Cost [Line Items]
Repurchase reserve							$ 100
Mortgage service fees	$ 800	$ 800	$ 1,500	$ 1,500
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	8,103		8,103
Residential loan
Servicing Asset at Amortized Cost [Line Items]
Proceeds from sale of mortgage loans	64,700	44,300	89,600	77,400
Gain on sale of mortgage loans	1,000	600	1,600	1,200
Servicing contracts
Servicing Asset at Amortized Cost [Line Items]
Gross carrying amount					$ 19,418	$ 18,556
Accumulated amortization					(11,315)	(10,494)
Valuation allowance	0	0	0	0	0	0	0
Net carrying amount					8,103	8,062	$ 8,509
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward]
Servicing asset - beginning balance	7,897	8,541	8,062	8,639
Amount capitalized	632	392	862	727
Amortization	(426)	(424)	(821)	(857)
Other-than-temporary impairment	0	0	0	0
Servicing asset - ending balance	8,103	8,509	8,103	8,509
Valuation Allowance [Roll Forward]
Valuation allowance, beginning balance	0	0	0	0
Provision (recovery)	0	0	0	0
Other-than-temporary impairment	0	0	0	0
Valuation allowance, ending balance	$ 0	$ 0	$ 0	$ 0
Unpaid principal balance					1,200,017	1,188,514
Prepayment rate:
25 basis points adverse rate change					(843)	(250)
50 basis points adverse rate change					(1,786)	(566)
Discount rate:
25 basis points adverse rate change					(108)	(139)
50 basis points adverse rate change					$ (215)	$ (275)
Servicing contracts | Note rate
Valuation Allowance [Roll Forward]
Weighted average measurement input					0.0401	0.0398
Servicing contracts | Discount rate
Valuation Allowance [Roll Forward]
Weighted average measurement input					0.093	0.100
Servicing contracts | Prepayment speed
Valuation Allowance [Roll Forward]
Weighted average measurement input					0.103	0.065