Bank segment - Mortgage servicing rights (Details) - American Savings Bank (ASB) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Servicing Asset at Amortized Cost [Line Items]
Repurchase reserve	$ 100	$ 100	$ 100	$ 100
Mortgage service fees	1,000	800	1,900	1,600
Mortgage servicing rights
Servicing asset - beginning balance			10,020
Servicing asset - ending balance	10,754		10,754
Residential loan
Servicing Asset at Amortized Cost [Line Items]
Proceeds from sale of residential loans	95,600	186,800	266,500	259,300
Gain on sale of mortgage loans	1,900	6,300	6,200	8,300
Servicing contracts
Changes in Carrying Value of MSRs
Gross carrying amount	21,865		21,865		$ 22,950
Accumulated amortization	(11,111)		(11,111)		(12,670)
Valuation allowance	0	(264)	0	(264)	(260)
Net carrying amount	10,754	9,647	10,754	9,647	10,020
Mortgage servicing rights
Servicing asset - beginning balance	10,689	9,120	10,280	9,101
Amount capitalized	1,023	1,726	2,570	2,362
Amortization	(958)	(935)	(2,096)	(1,552)
Other-than-temporary impairment	0	0	0	0
Servicing asset - ending balance	10,754	9,911	10,754	9,911
Valuation allowance for mortgage servicing rights
Valuation allowance, beginning balance	4	0	260	0
Provision	(4)	264	(260)	264
Other-than-temporary impairment	0	0	0	0
Valuation allowance, ending balance	0	$ 264	0	$ 264
Unpaid principal balance	1,535,932		1,535,932		1,450,312
Prepayment rate:
25 basis points adverse rate change	(771)		(771)		(738)
50 basis points adverse rate change	(1,738)		(1,738)		(1,445)
Discount rate:
25 basis points adverse rate change	(120)		(120)		(68)
50 basis points adverse rate change	$ (238)		$ (238)		$ (135)
Servicing contracts | Note rate
Valuation allowance for mortgage servicing rights
Weighted average measurement input	0.0347		0.0347		0.0368
Servicing contracts | Discount rate
Valuation allowance for mortgage servicing rights
Weighted average measurement input	0.0925		0.0925		0.0925
Servicing contracts | Prepayment speed
Valuation allowance for mortgage servicing rights
Weighted average measurement input	0.113		0.113		0.177