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Securities, Held to Maturity (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | $ 678,435 |  | $ 678,435 |  | $ 783,599
Unrealized gains | 13,324 |  | 13,324 |  | 3,362
Unrealized losses | 570 |  | 570 |  | 8,286
Estimated fair value | 691,189 |  | 691,189 |  | 778,675
Gains from calls on HTM securities | 4 | $ 0 | 4 | $ 0 |
Amortized costs of securities available for sale and held to maturity pledged to secure public deposits | 1,400,000 |  | 1,400,000 |  | 1,500,000
Amortized costs of securities AFS and HTM pledged as collateral for repurchase agreements | 186,300 |  | 186,300 |  | 215,300
Federal Agency [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 10,000 |  | 10,000 |  | 19,995
Unrealized gains | 6 |  | 6 |  | 52
Unrealized losses | 0 |  | 0 |  | 0
Estimated fair value | 10,006 |  | 10,006 |  | 20,047
Mortgage-Backed, Government Sponsored Enterprises [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 154,701 |  | 154,701 |  | 164,618
Unrealized gains | 3,139 |  | 3,139 |  | 712
Unrealized losses | 127 |  | 127 |  | 2,773
Estimated fair value | 157,713 |  | 157,713 |  | 162,557
Mortgage-Backed, U.S. Government Agency Securities [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 13,679 |  | 13,679 |  | 15,230
Unrealized gains | 785 |  | 785 |  | 403
Unrealized losses | 0 |  | 0 |  | 0
Estimated fair value | 14,464 |  | 14,464 |  | 15,633
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 213,409 |  | 213,409 |  | 257,475
Unrealized gains | 2,849 |  | 2,849 |  | 1,097
Unrealized losses | 365 |  | 365 |  | 3,897
Estimated fair value | 215,893 |  | 215,893 |  | 254,675
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 112,974 |  | 112,974 |  | 83,148
Unrealized gains | 4,001 |  | 4,001 |  | 767
Unrealized losses | 64 |  | 64 |  | 0
Estimated fair value | 116,911 |  | 116,911 |  | 83,915
State & Municipal [Member] |  |  |  |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |  |  |  |
Amortized cost | 173,672 |  | 173,672 |  | 243,133
Unrealized gains | 2,544 |  | 2,544 |  | 331
Unrealized losses | 14 |  | 14 |  | 1,616
Estimated fair value | $ 176,202 |  | $ 176,202 |  | $ 241,848

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- Definition This represents the available for sale and held to maturity securities that are pledged as collateral to secure public deposits and for other purposes required or permitted by law. + References No definition available. + Details
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