Disclosures about Fair Value of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Disclosures about Fair Value of Assets and Liabilities
Trading securities	$ 227,914	$ 163,419
Available for sale securities	308,673	331,071
Loans held for sale	23,357	11,886
Mortgage servicing rights	71,989	77,844
Recurring
Disclosures about Fair Value of Assets and Liabilities
Trading securities	227,914	163,419
Loans held for sale	23,357	11,886
Mortgage servicing rights	71,989	77,844
Recurring \| Interest Rate Lock Commitments
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	296	70
Derivative liabilities	8
Recurring \| Forward Contracts
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	14
Derivative liabilities	16	9
Recurring \| Interest rate swaps
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	48
Derivative liabilities	48
Level 2 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Trading securities	227,914	163,419
Loans held for sale	23,357	11,886
Level 2 \| Recurring \| Forward Contracts
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	14
Derivative liabilities	16	9
Level 2 \| Recurring \| Interest rate swaps
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	48
Derivative liabilities	48
Level 3 \| Interest Rate Lock Commitments
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	296	70
Derivative liabilities	8
Level 3 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Mortgage servicing rights	71,989	77,844
Level 3 \| Recurring \| Interest Rate Lock Commitments
Disclosures about Fair Value of Assets and Liabilities
Derivative assets	296	70
Derivative liabilities	8
Treasury notes \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	2,765	11,941
Treasury notes \| Level 1 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	2,765	11,941
Federal agencies
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	257,388	236,930
Federal agencies \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	257,388	236,930
Federal agencies \| Level 2 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	257,388	236,930
Municipals \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	12,760	21,332
Municipals \| Level 2 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	12,760	21,332
Mortgage-backed - Government-sponsored entity (GSE) - residential
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	35,760	60,868
Mortgage-backed - Government-sponsored entity (GSE) - residential \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	35,760	60,868
Mortgage-backed - Government-sponsored entity (GSE) - residential \| Level 2 \| Recurring
Disclosures about Fair Value of Assets and Liabilities
Available for sale securities	$ 35,760	$ 60,868

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
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-Name Accounting Standards Codification
-Topic 825
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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Section 45
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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section S99
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