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Derivatives and Balance Sheet Offsetting (Tables) | 9 Months Ended
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Sep. 30, 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
September 30, 2018 | (in thousands)
Assets |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 10,479 |  |  | $ | — |  |  | $ | 10,479 |  |  | $ | — |  |  | $ | 10,479 |
Liabilities |  |  |  |  |  |  |  |  |
Interest rate contracts | $ | 10,478 |  |  | $ | — |  |  | $ | 10,478 |  |  | $ | (9,595 | ) |  | $ | 883 |
Repurchase agreements | $ | 62,197 |  |  | $ | — |  |  | $ | 62,197 |  |  | $ | (62,197 | ) |  | $ | — |
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 | ) |  | $ | — |
Carrying Value of Securities Pledged As Collateral | The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:
|  | September 30, 2018
|  | (in thousands)
Washington and Oregon State to secure public deposits |  | $ | 256,078 |
Federal Reserve Bank to secure borrowings |  | 51,843 |
Other securities pledged |  | 119,981 |
Total securities pledged as collateral |  | $ | 427,902 |
Not Designated as Hedging Instrument [Member] |
Derivative [Line Items] |
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value | The following table presents the fair value of derivatives not designated as hedging instruments at September 30, 2018 and December 31, 2017:
| Asset Derivatives |  | Liability Derivatives
| September 30, 2018 |  | December 31, 2017 |  | September 30, 2018 |  | December 31, 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 |  | $ | 10,479 |  |  | Other assets |  | $ | 6,707 |  |  | Other liabilities |  | $ | 10,478 |  |  | Other liabilities |  | $ | 6,714 |
Available-for-sale Securities [Member] |
Derivative [Line Items] |
Carrying Value of Securities Pledged As Collateral | 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
September 30, 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 |  | $ | 62,197 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 62,197 |
Gross amount of recognized liabilities for repurchase agreements |  |  |  |  |  |  |  |  |  | 62,197 |
Amounts related to agreements not included in offsetting disclosure |  |  |  |  |  |  |  |  |  | $ | — |

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- Definition Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 + Details
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