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Securities (Tables) | 12 Months Ended
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Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items] |
Securities Available for Sale | The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of debt securities available for sale:
|  | Amortized Cost |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
December 31, 2018 |  | (in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 2,222,521 |  |  | $ | 9,236 |  |  | $ | (43,467 | ) |  | $ | 2,188,290 |
State and municipal securities |  | 579,755 |  |  | 2,328 |  |  | (7,760 | ) |  | 574,323 |
U.S. government agency and government-sponsored enterprise securities |  | 408,088 |  |  | 1,235 |  |  | (4,736 | ) |  | 404,587 |
U.S. government securities |  | 251 |  |  | — |  |  | (3 | ) |  | 248 |
Total |  | $ | 3,210,615 |  |  | $ | 12,799 |  |  | $ | (55,966 | ) |  | $ | 3,167,448 |
December 31, 2017 |  |  |  |  |  |  |  |
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 1,752,236 |  |  | $ | 1,815 |  |  | $ | (27,326 | ) |  | $ | 1,726,725 |
State and municipal securities |  | 593,940 |  |  | 6,023 |  |  | (3,959 | ) |  | 596,004 |
U.S. government agency and government-sponsored enterprise securities |  | 416,894 |  |  | 642 |  |  | (2,762 | ) |  | 414,774 |
U.S. government securities |  | 251 |  |  | — |  |  | (3 | ) |  | 248 |
Total |  | $ | 2,763,321 |  |  | $ | 8,480 |  |  | $ | (34,050 | ) |  | $ | 2,737,751 |
Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table Text Block] | The following table provides the proceeds and both gross realized gains and losses on the sales and calls of debt securities available for sale as well as other securities gains and losses for the periods indicated:
|  | Years Ended December 31,
|  | 2018 |  | 2017 |  | 2016
|  | (in thousands)
Proceeds from sales and calls of debt securities available for sale |  | $ | 32,330 |  |  | $ | 30,403 |  |  | $ | 124,142 |
Gross realized gains from sales of debt securities available for sale |  | $ | 235 |  |  | $ | 111 |  |  | $ | 1,181 |
Gross realized losses from sales of debt securities available for sale |  | (129 | ) |  | (122 | ) |  | — |
Other securities losses, net (1) |  | (195 | ) |  | — |  |  | — |
Investment securities gains (losses), net |  | $ | (89 | ) |  | $ | (11 | ) |  | $ | 1,181 |
__________ (1) Other securities losses, net includes net unrealized loss activity associated with equity securities.
Unrealized Gain (Loss) on Investments [Table Text Block] | The following table provides the unrealized gains and losses on equity securities at the reporting date:
|  | Year Ended December 31,
|  | 2018
|  | (in thousands)
Net gains and losses recognized during the period on equity securities |  | $ | 195 |
Less: Net gains and losses recognized during the period on equity securities sold during the period. |  | (195 | )
Unrealized gains and losses recognized during the reporting period on equity securities still held at the reporting date. |  | $ | — |
Schedule of Contractual Maturities of Investment Securities Available for Sale | The scheduled contractual maturities of debt securities available for sale at December 31, 2018 are presented as follows:
|  | December 31, 2018
|  | Amortized Cost |  | Fair Value
|  | (in thousands)
Due within one year |  | $ | 130,592 |  |  | $ | 130,241 |
Due after one year through five years |  | 566,382 |  |  | 559,600 |
Due after five years through ten years |  | 1,398,135 |  |  | 1,391,517 |
Due after ten years |  | 1,115,506 |  |  | 1,086,090 |
Total debt securities available for sale |  | $ | 3,210,615 |  |  | $ | 3,167,448 |
Schedule of Securities pledged as collateral [Table Text Block] | 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:
|  | December 31,
|  | 2018 |  | 2017
|  | (in thousands)
Washington and Oregon State to secure public deposits |  | $ | 276,343 |  |  | $ | 245,222 |
Federal Reserve Bank to secure borrowings |  | 52,303 |  |  | 52,917 |
Other securities pledged |  | 138,492 |  |  | 121,244 |
Total securities pledged as collateral |  | $ | 467,138 |  |  | $ | 419,383 |
Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses | The following tables show the gross unrealized losses and fair value of the Company’s debt securities available for sale with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2018 and 2017:
|  | Less than 12 Months |  | 12 Months or More |  | Total
|  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses |  | Fair Value |  | Unrealized Losses
December 31, 2018 |  | (in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 154,622 |  |  | $ | (972 | ) |  | $ | 1,301,387 |  |  | $ | (42,495 | ) |  | $ | 1,456,009 |  |  | (43,467 | )
State and municipal securities |  | 106,292 |  |  | (581 | ) |  | 280,496 |  |  | (7,179 | ) |  | 386,788 |  |  | (7,760 | )
U.S. government agency and government-sponsored enterprise securities |  | 15,392 |  |  | (45 | ) |  | 291,435 |  |  | (4,691 | ) |  | 306,827 |  |  | (4,736 | )
U.S. government securities |  | — |  |  | — |  |  | 247 |  |  | (3 | ) |  | 247 |  |  | (3 | )
Total |  | $ | 276,306 |  |  | $ | (1,598 | ) |  | $ | 1,873,565 |  |  | $ | (54,368 | ) |  | $ | 2,149,871 |  |  | $ | (55,966 | )
December 31, 2017 |  |  |  |  |  |  |  |  |  |  |  |
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations |  | $ | 816,678 |  |  | $ | (6,710 | ) |  | $ | 717,211 |  |  | $ | (20,616 | ) |  | $ | 1,533,889 |  |  | $ | (27,326 | )
State and municipal securities |  | 220,019 |  |  | (1,723 | ) |  | 75,172 |  |  | (2,236 | ) |  | 295,191 |  |  | (3,959 | )
U.S. government agency and government-sponsored enterprise securities |  | 184,046 |  |  | (1,006 | ) |  | 155,983 |  |  | (1,756 | ) |  | 340,029 |  |  | (2,762 | )
U.S. government securities |  | 249 |  |  | (3 | ) |  | — |  |  | — |  |  | 249 |  |  | (3 | )
Total |  | $ | 1,220,992 |  |  | $ | (9,442 | ) |  | $ | 948,366 |  |  | $ | (24,608 | ) |  | $ | 2,169,358 |  |  | $ | (34,050 | )

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- Definition Schedule of amortized cost and fair value of the debt securities available for sale portfolio of the entity by contractual maturity. The table includes maturity categories of: due in one year or less; due after one year through five years; due after five years through ten years; and due after ten years. A single line item is provided for "total securities with no stated maturity" in order for the total line item of the table to match total available for sale securities. + References No definition available. + Details
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- Definition Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities. + References No definition available. + Details
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