Disclosures about Fair Value of Assets and Liabilities - Quantitative Information about Unobservable Inputs (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Quantitative information about unobservable inputs
Mortgage servicing rights	$ 71,490	$ 66,079
Available for sale securities	269,709	408,371
Interest Rate Lock Commitments \| Level 3
Quantitative information about unobservable inputs
Derivative assets	68
Mortgage servicing rights \| Level 3
Quantitative information about unobservable inputs
Mortgage servicing rights	$ 71,490	$ 66,079
Mortgage servicing rights \| Level 3 \| Minimum
Quantitative information about unobservable inputs
Discount rate (as a percent)	8.00%	8.00%
Constant prepayment rate (as a percent)	1.00%	1.00%
Mortgage servicing rights \| Level 3 \| Maximum
Quantitative information about unobservable inputs
Discount rate (as a percent)	13.00%	13.00%
Constant prepayment rate (as a percent)	29.00%	36.00%
Collateral-dependent impaired loans \| Level 3
Quantitative information about unobservable inputs
Collateral-dependent impaired loans	$ 149	$ 2,126
Marketability discount (as a percent)	60.00%
Collateral-dependent impaired loans \| Level 3 \| Minimum
Quantitative information about unobservable inputs
Marketability discount (as a percent)		5.00%
Collateral-dependent impaired loans \| Level 3 \| Maximum
Quantitative information about unobservable inputs
Marketability discount (as a percent)		47.00%
Municipals
Quantitative information about unobservable inputs
Available for sale securities		$ 6,688
Measurement Input, Maturity \| Interest Rate Lock Commitments \| Level 3 \| Minimum
Quantitative information about unobservable inputs
Loan closing rates (as a percent)	73.00%
Loan closing rates (as a percent)	73.00%
Measurement Input, Maturity \| Interest Rate Lock Commitments \| Level 3 \| Maximum
Quantitative information about unobservable inputs
Loan closing rates (as a percent)	99.00%
Loan closing rates (as a percent)	99.00%

Value of input used to measure derivative asset.

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- Definition

Value of input used to measure derivative liability.

+ References

No definition available.

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- Definition

It is a rate of marketability discount under fair value inputs.

+ References

No definition available.

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- Definition

The fair value amount of impaired loans.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

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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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

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- Definition

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

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