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Derivative Instruments - Narrative (Details) | 1 Months Ended |  |  |  |
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Jun. 30, 2014 USD ($) derivative_instrument | Sep. 30, 2018 USD ($) | Apr. 30, 2018 USD ($) | Dec. 31, 2017 USD ($) | Apr. 30, 2012 USD ($) derivative_instrument
Interest rate contracts with corporate customers |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount |  | $ 204,100,000 |  |  |
Offsetting interest rate contracts with other financial institutions |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount |  | 204,100,000 |  |  |
Interest rate swaps |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Number of instruments held | derivative_instrument | 2 |  |  |  |
Floating rate liability at the bank level, derivative one |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount | $ 15,000,000 |  |  |  |
Term of contract | 4 years |  |  |  |
Floating rate liability at the bank level, derivative two |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount | $ 15,000,000 |  |  |  |
Term of contract | 5 years |  |  |  |
Cash flow hedging |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount |  |  | $ 30,000,000 |  | $ 32,000,000
Number of instruments held | derivative_instrument |  |  |  |  | 2
Commitments to fund fixed-rate residential mortgage loans |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount |  | 236,932,000 |  | $ 131,000,000 |
Commitments to sell residential mortgage loans |  |  |  |  |
Derivative Instruments (Textual) [Abstract] |  |  |  |  |
Notional amount |  | $ 381,089,000 |  | $ 199,000,000 |

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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 + Details
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- Definition Derivative instruments. + References No definition available. + Details
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- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959 + Details
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- Definition Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Details
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