Mortgage Banking Activities, Components of Loans Held For Sale (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
Number of days for past due for loan to be considered nonperforming (in days)	90 days	90 days	90 days
Residential mortgage loans held for sale, nonperforming	$ 0	$ 0	$ 0
Credit losses recognized on residential mortgage loans held for sale	0	0	0
Components of Residential Mortgage Loans Held for Sale [Abstract]
Unpaid principal balance	169,095	261,868	212,525
Residential mortgage loans held for sale, Fair value	169,226	265,783	215,113
Total residential mortgage loans held for sale and mortgage loan commitments, net of forward sales contracts	$ 175,866	$ 275,643	$ 221,378
Residential Mortgage Loan Commitments [Member] \| Not Designated as Hedging Instrument [Member]
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
General number of days outstanding for residential mortgage commitments, minimum (in days)	60 days	60 days	60 days
General number of days outstanding for residential mortgage commitments, maximum (in days)	90 days	90 days	90 days
Components of Residential Mortgage Loans Held for Sale [Abstract]
Notional	$ 197,752	$ 334,337	$ 222,919
Derivative, Net fair value	$ 5,027	$ 9,066	$ 6,523
Forward sales contracts [Member] \| Not Designated as Hedging Instrument [Member]
Schedule of Residential Mortgage Loans Held For Sale [Line Items]
General number of days for delivery of loans, for which the price is set by forward sales contracts, minimum (in days)	60 days	60 days	60 days
General number of days for delivery for loans, for which the price is set by forward sales contracts, maximum (in days)	90 days	90 days	90 days
Components of Residential Mortgage Loans Held for Sale [Abstract]
Notional	$ 330,876	$ 524,878	$ 380,159
Derivative, Net fair value	$ 1,613	$ 794	$ (258)

Represents the individual components of residential mortgage loans held for sale

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- Definition

Credit losses recognized on residential mortgage loans held for sale

+ References

No definition available.

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- Definition

Represents the fair value of residential mortgage loans held for sale as of the balance sheet, exclusive of mortgage commitments and forward sales contracts

+ References

No definition available.

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- Definition

Represents represents the typical maximum period for commitment to originate a residential mortgage loan to when the closed loan is sold to an investor.

+ References

No definition available.

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Represents represents the typical maximum number of days from the point pricing is set to delivery of forward sales contracts.

+ References

No definition available.

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- Definition

Represents represents the typical minimum period for commitment to originate a residential mortgage loan to when the closed loan is sold to an investor.

+ References

No definition available.

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Represents the minimum number of days from the point of pricing being set to delivery of forward sales contracts.

+ References

No definition available.

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- Definition

Represents the number of days past due for residential mortgage loans held for sale to be reported as delinquent.

+ References

No definition available.

+ Details

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- Definition

Residential mortgage loans held for sale, 90 days past due or impaired.

+ References

No definition available.

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- Definition

Unpaid principal balance of loans held for sale.

+ References

No definition available.

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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

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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- Definition

Amount, after allowance for bad debt, of mortgage loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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