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Derivatives and Balance Sheet Offsetting (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Derivative [Line Items] |  |  |  |  |
Gain (Loss) on Derivative Instruments, Net, Pretax | $ 2 | $ 2 | $ 8 | $ 6 |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 46,229 |  | 46,229 |  |
Secured Borrowings, Gross, Difference, Amount | 0 |  | 0 |  |
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 46,229 |  | 46,229 |  |
Maturity Overnight [Member] | U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 46,229 |  | 46,229 |  |
Maturity Less than 30 Days [Member] | U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 0 |  | 0 |  |
Maturity 30 to 90 Days [Member] | U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 0 |  | 0 |  |
Maturity Greater than 90 Days [Member] | U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 0 |  | 0 |  |
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, Notional Amount | 368,400 |  | 368,400 |  | $ 384,700
Not Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest Rate Contracts [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Fair value of asset derivative instruments | 8,624 |  | 8,624 |  | 6,707
Not Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest Rate Contracts [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Fair value of liability derivative instruments | $ 8,624 |  | $ 8,624 |  | $ 6,714

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