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Derivatives and Balance Sheet Offsetting Balance Sheet Offsetting (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Balance Sheet Offsetting [Line Items] |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | $ 24,247 |
Repurchase agreements, amounts offset in balance sheet | 0 | $ 0
Repurchase agreements, net amount presented in statement of financial position | 24,247 | 79,059
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities | (24,247) | (79,059)
Securities sold under agreements to repurchase, amount not offset | 0 | 0
Interest Rate Contracts [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Derivative Assets, Gross Amounts Offset in the Balance Sheets | 0 | 0
Derivative Asset | 7,406 | 6,707
Derivative, Collateral, Obligation to Return Securities | 0 | 0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral | 7,406 | 6,707
Derivative Liability, Gross Amounts Offset in Balance Sheets | 0 | 0
Derivative Liability | 7,409 | 6,714
Derivative, Collateral, Right to Reclaim Securities | (1,190) | (6,714)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral | 6,219 | 0
Available-for-sale Securities [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Securities Sold under Agreements to Repurchase, Gross | 24,247 | 79,059
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Assets [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Fair value of asset derivative instruments | 7,406 | 6,707
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member] | Other Liabilities [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Fair value of liability derivative instruments | 7,409 | $ 6,714
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | 24,247 |
Maturity Overnight [Member] | U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |
Balance Sheet Offsetting [Line Items] |  |
Secured Borrowings, Gross Including Not Subject to Master Netting Arrangement | $ 24,247 |

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