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Derivatives and Balance Sheet Offsetting (Tables) | 12 Months Ended
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Dec. 31, 2018
Derivative [Line Items] |
Balance Sheet Offsetting [Table Text Block] | The following tables show the gross interest rate swap agreements and repurchase agreements in the Consolidated Balance Sheets and the respective collateral received or pledged in the form of cash or other financial instruments, which are generally marketable securities. The collateral amounts in these tables are limited to the outstanding balances of the related asset or liability. Therefore, instances of overcollateralization are not shown.
| Gross Amounts of Recognized Assets/Liabilities |  | Gross Amounts Offset in the Consolidated Balance Sheets |  | Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets |  | Gross Amounts Not Offset in the Consolidated Balance Sheets
|  |  |  | Collateral Posted |  | Net Amount
December 31, 2018 | (in thousands)
Assets |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 7,033 |  |  | $ | — |  |  | $ | 7,033 |  |  | $ | — |  |  | $ | 7,033 |
Liabilities |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 7,033 |  |  | $ | — |  |  | $ | 7,033 |  |  | $ | (3,235 | ) |  | $ | 3,798 |
Repurchase agreements | $ | 61,094 |  |  | $ | — |  |  | $ | 61,094 |  |  | $ | (61,094 | ) |  | $ | — |
December 31, 2017 |  |  |  |  |  |  |  |  |
Assets |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 6,707 |  |  | $ | — |  |  | $ | 6,707 |  |  | $ | — |  |  | $ | 6,707 |
Liabilities |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 6,714 |  |  | $ | — |  |  | $ | 6,714 |  |  | $ | (6,714 | ) |  | $ | — |
Repurchase agreements | $ | 79,059 |  |  | $ | — |  |  | $ | 79,059 |  |  | $ | (79,059 | ) |  | $ | — |
Not Designated as Hedging Instrument [Member] |
Derivative [Line Items] |
Schedule of Fair Value Derivative Instruments | The following table presents the fair value and balance sheet classification of derivatives not designated as hedging instruments at December 31, 2018 and 2017:
| Asset Derivatives |  | Liability Derivatives
| 2018 |  | 2017 |  | 2018 |  | 2017
| Balance Sheet Location |  | Fair Value |  | Balance Sheet Location |  | Fair Value |  | Balance Sheet Location |  | Fair Value |  | Balance Sheet Location |  | Fair Value
|  |  | (in thousands) |  |
Interest rate contracts | Other assets |  | $ | 7,033 |  |  | Other assets |  | $ | 6,707 |  |  | Other liabilities |  | $ | 7,033 |  |  | Other liabilities |  | $ | 6,714 |
Available-for-sale Securities [Member] |
Derivative [Line Items] |
Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block] | The following table presents the class of collateral pledged for repurchase agreements as well as the remaining contractual maturity of the repurchase agreements:
|  | Remaining contractual maturity of the agreements
|  | Overnight and continuous |  | Up to 30 days |  | 30 - 90 days |  | Greater than 90 days |  | Total
December 31, 2018 |  | (in thousands)
Class of collateral pledged for repurchase agreements |  |  |  |  |  |  |  |  |  |
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 61,094 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 61,094 |
Gross amount of recognized liabilities for repurchase agreements |  | 61,094 |
Amounts related to agreements not included in offsetting disclosure |  | $ | — |

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