Loans - Troubled Debt Restructuring and Loans Accounted for Under ASC Topic 310-30 Narratives (Details) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($) item	Mar. 31, 2017 loan
Troubled Debt Restructurings [Member]
Debt Instrument [Line Items]
TDR's modified within the past year that defaulted on their restructured terms	1	0
Number of restructured loans \| item	4
Recorded investment \| $	$ 0.9
Agriculture and Consumer loans [Member]
Debt Instrument [Line Items]
TDR's modified within the past year that defaulted on their restructured terms \| item	1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment \| $	$ 0.2

Troubled Debt Restructuring Number Of Loans Restructured

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.

+ Details

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- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

+ Details

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

+ Details

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- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

+ Details

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