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Fair Value Measurements and Fair Value of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Financial assets [Abstract] |  |
HTM securities | $ 782,761 | $ 778,675
Carrying Amount [Member] | Level 2 [Member] |  |
Financial assets [Abstract] |  |
HTM securities | 780,565 | 783,599
Financial liabilities [Abstract] |  |
Time deposits | 922,304 | 930,678
Long-term debt | 73,696 | 73,724
Junior subordinated debt | 101,196 | 101,196
Carrying Amount [Member] | Level 3 [Member] |  |
Financial assets [Abstract] |  |
Net loans | 6,827,432 | 6,822,147
Estimated Fair Value [Member] | Level 2 [Member] |  |
Financial assets [Abstract] |  |
HTM securities | 782,761 | 778,675
Financial liabilities [Abstract] |  |
Time deposits | 915,990 | 920,534
Long-term debt | 73,981 | 73,927
Junior subordinated debt | 102,946 | 100,114
Estimated Fair Value [Member] | Level 3 [Member] |  |
Financial assets [Abstract] |  |
Net loans | $ 6,775,550 | $ 6,754,460

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