Bank segment - Mortgage servicing rights (Details) - American Savings Bank (ASB) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 31, 2015 USD ($) loan	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)
Servicing Asset at Amortized Cost [Line Items]
Mortgage service fees		$ 900	$ 900	$ 2,700	$ 2,600
Movement in Mortgage Loans on Real Estate [Roll Forward]
Servicing Asset at Amortized Cost	$ 12,258			11,540
Servicing Asset at Amortized Cost		12,258		12,258		$ 11,540
Mortgage Servicing Rights (MSR)
Servicing Asset at Amortized Cost [Line Items]
Gross carrying amount							$ 29,818		$ 26,685
Accumulated amortization							(17,560)		(15,003)
Valuation allowance	0	0	(158)	(209)	(251)	(251)	0	$ (209)	(158)
Net carrying amount							12,258		$ 11,524
Movement in Mortgage Loans on Real Estate [Roll Forward]
Servicing Asset at Amortized Cost	12,258			11,749	11,938	11,938
Servicing Asset at Amortized Value, Amount Capitalized				2,636	1,098
Servicing Asset at Amortized Cost, Amortization				(2,123)	(1,297)
Other-than-temporary impairment				(4)	(57)
Servicing Asset at Amortized Cost		12,258	11,682	12,258	11,682	11,749
Valuation Allowance [Roll Forward]
Valuation allowance, beginning balance	$ 0			209	251	251
Provision (recovery)				(205)	(36)
Other-than-temporary impairment				(4)	(57)
Valuation allowance, ending balance		$ 0	$ 158	$ 0	$ 158	$ 209
Unpaid principal balance							1,503,369	1,391,030
Weighted average note-rate				4.01%		4.07%
Weighted average discount rate				9.50%		9.60%
Weighted average prepayment speed				9.90%		9.50%
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 25 Basis Point Adverse Change in Prepayment Speed							(832)	(757)
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 50 Basis Point Adverse Change in Prepayment Speed							(1,643)	(1,524)
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 25 Basis Points Adverse Change in Discount Rate							(148)	(140)
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of 50 Basis Points Adverse Change in Discount Rate							$ (293)	$ (278)
Mortgage Servicing Rights (MSR) | Residential loan | Subsequent Event
Valuation Allowance [Roll Forward]
Mortgage servicing rights, underlying loans disposed | loan	1,500
Unpaid principal balance of loans	$ 419,000