Mortgage servicing rights - Schedule of Changes in Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Servicing Asset at Fair Value, Amount [Roll Forward]
Carrying value prior to policy change	$ 76,107	$ 32,070	$ 29,711
Fair value impact of change in accounting policy (See Note 1)	0	1,011	0
Carrying value at beginning of period	76,107	33,081	29,711
Capitalization	54,913	58,984	46,070
Amortization	0	0	(8,321)
Sales	(39,428)	(11,686)	(34,118)
(Loss) gain on sale	0	(249)	3,406
Impairment	0	0	(4,678)
Change in fair value:
Due to pay-offs/pay-downs	(11,062)	(3,104)	0
Due to change in valuation inputs or assumptions	8,299	(919)	0
Carrying value at December 31	$ 88,829	$ 76,107	$ 32,070

Servicing asset amortized value to fair value adjustment.

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- Definition

Servicing asset at amortized value gain (loss) on sale.

+ References

No definition available.

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Servicing asset at fair value, changes in fair value due to pay-offs or pay-downs.

+ References

No definition available.

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- Definition

Amount of other-than-temporary impairment (OTTI) applied to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

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Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amount of amortization of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Amount conveyed to unrelated parties of contract to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of increase (decrease) in fair value from changes in the inputs, assumptions, or model used to calculate the fair value of the contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

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