Bank segment - Mortgage servicing rights (Details) - American Savings Bank (ASB) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Servicing Asset at Amortized Cost [Line Items]
Repurchase reserve	$ 100	$ 100	$ 100	$ 100
Mortgage service fees	1,000	900	2,800	2,500
Mortgage servicing rights
Servicing asset - beginning balance			10,020
Servicing asset - ending balance	10,272		10,272
Residential loan
Servicing Asset at Amortized Cost [Line Items]
Proceeds from sale of residential loans	38,300	128,000	304,800	387,200
Gain on sale of mortgage loans	1,300	7,700	7,500	15,900
Servicing contracts
Changes in Carrying Value of MSRs
Gross carrying amount	22,182		22,182		$ 22,950
Accumulated amortization	(11,910)		(11,910)		(12,670)
Valuation allowance	0	(382)	0	(382)	(260)
Net carrying amount	10,272	9,553	10,272	9,553	10,020
Mortgage servicing rights
Servicing asset - beginning balance	10,754	9,911	10,280	9,101
Amount capitalized	315	1,119	2,885	3,481
Amortization	(797)	(1,095)	(2,893)	(2,647)
Other-than-temporary impairment	0	0	0	0
Servicing asset - ending balance	10,272	9,935	10,272	9,935
Valuation allowance for mortgage servicing rights
Valuation allowance, beginning balance	0	264	260	0
Provision	0	118	(260)	382
Other-than-temporary impairment	0	0	0	0
Valuation allowance, ending balance	0	$ 382	0	$ 382
Unpaid principal balance	1,521,966		1,521,966		1,450,312
Prepayment rate:
25 basis points adverse rate change	(1,045)		(1,045)		(738)
50 basis points adverse rate change	(2,209)		(2,209)		(1,445)
Discount rate:
25 basis points adverse rate change	(115)		(115)		(68)
50 basis points adverse rate change	$ (229)		$ (229)		$ (135)
Servicing contracts | Note rate
Valuation allowance for mortgage servicing rights
Weighted average measurement input	0.0342		0.0342		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	0.117		0.117		0.177