Mortgage Servicing Rights - Loans, Fees, Amortization and Carrying Value (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Other Intangible Assets
Unpaid principal amount of consumer loans serviced for others	$ 2,600,000		$ 2,700,000
Contractually specified fees, late charges, and ancillary fees	1,600	$ 1,700
Amortization of mortgage servicing rights	764	988
MSRs
Other Intangible Assets
Amortization of mortgage servicing rights	800	$ 1,000
Estimated future amortization expenses
Under one year	2,236
One to two years	1,968
Two to three years	1,733
Three to four years	1,523
Four to five years	1,339
Details of mortgage servicing rights
Gross carrying amount	63,350		63,342
Less: accumulated amortization	47,951		47,187
Net carrying value	$ 15,399		$ 16,155

Principal amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction. Continuing involvement includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets.

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Amount of contractually specified servicing fee, late fee, and ancillary fee recognized as income for servicing asset and servicing liability.

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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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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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