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Securities - Narrative (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2017 USD ($) security institution | Sep. 30, 2016 USD ($) | Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Transferred security, at carrying value | $ 365,941,000 |  | $ 365,941,000 |  |
Unrealized gain (loss) on transfer | 13,218,000 |  |  |  |
Gains on sales of securities available for sale, net | 57,000 | $ 0 | 57,000 | $ 1,186,000 |
Amortized cost | 1,141,627,000 |  | 1,141,627,000 |  | $ 686,405,000
Gross gains on sales of securities available for sale | 57,000 | 0 | 57,000 | 1,257,000 |
Securities available for sale | 1,150,459,000 |  | $ 1,150,459,000 |  | 674,248,000
Number of institutions issuing debt (more than) | institution |  |  | 160 |  |
Trust preferred securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Amortized cost | 12,454,000 |  | $ 12,454,000 |  | 23,749,000
Securities available for sale | 8,960,000 |  | $ 8,960,000 |  | 18,389,000
Number of securities representing interests in tranches of trusts (tranches) | security |  |  | 2 |  |
Impairments |  |  | $ 0 |  |
Secure government, public and trust deposits |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale securities pledged as collateral | 459,369,000 |  | 459,369,000 |  | 642,447,000
Short-term borrowings |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale securities pledged as collateral | 27,164,000 |  | 27,164,000 |  | 24,426,000
Trust preferred securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 9,346,000 |  | 9,346,000 |  |
Sale proceeds | 9,403,000 |  |  |  |
Amortized cost | 12,454,000 |  | 12,454,000 |  | 23,749,000
Securities available for sale | 8,960,000 |  | 8,960,000 |  | 18,389,000
Residential mortgage-backed securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 2,946,000 |  | 2,946,000 |  |
Sale proceeds |  |  | 2,946,000 |  |
Other equity securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Sale proceeds |  |  |  | 4,028,000 |
Amortized cost |  | $ 2,842,000 |  | 2,842,000 |
Gross gains on sales of securities available for sale |  |  |  | $ 1,186,000 |
Government agency mortgage backed securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 14,750,000 |  | 14,750,000 |  |
Government agency mortgage backed securities | Residential mortgage-backed securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 459,336,000 |  | 459,336,000 |  |
Amortized cost | 459,336,000 |  | 459,336,000 |  | 414,019,000
Securities available for sale | 459,558,000 |  | 459,558,000 |  | 409,317,000
Government agency collateralized mortgage obligations |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 16,395,000 |  | 16,395,000 |  |
Government agency collateralized mortgage obligations | Residential mortgage-backed securities |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 234,224,000 |  | 234,224,000 |  |
Amortized cost | 234,224,000 |  | 234,224,000 |  | 171,362,000
Securities available for sale | 232,658,000 |  | 232,658,000 |  | $ 168,826,000
Obligations of states and political subdivisions |  |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |  |
Available for sale debt securities | 4,876,000 |  | 4,876,000 |  |
Amortized cost | 337,725,000 |  | 337,725,000 |  |
Securities available for sale | $ 350,354,000 |  | $ 350,354,000 |  |

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