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Securities, Held to Maturity (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
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Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | $ 780,565 | $ 783,599
Unrealized gains | 5,767 | 3,362
Unrealized losses | 3,571 | 8,286
Estimated fair value | 782,761 | 778,675
Amortized costs of securities available for sale and held to maturity pledged to secure public deposits | 1,500,000 | 1,500,000
Amortized costs of securities AFS and HTM pledged as collateral for repurchase agreements | 207,500 | 215,300
Federal Agency [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 19,995 | 19,995
Unrealized gains | 55 | 52
Unrealized losses | 0 | 0
Estimated fair value | 20,050 | 20,047
Mortgage-Backed, Government Sponsored Enterprises [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 160,566 | 164,618
Unrealized gains | 1,281 | 712
Unrealized losses | 981 | 2,773
Estimated fair value | 160,866 | 162,557
Mortgage-Backed, U.S. Government Agency Securities [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 14,545 | 15,230
Unrealized gains | 460 | 403
Unrealized losses | 0 | 0
Estimated fair value | 15,005 | 15,633
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 247,418 | 257,475
Unrealized gains | 1,388 | 1,097
Unrealized losses | 2,230 | 3,897
Estimated fair value | 246,576 | 254,675
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 103,741 | 83,148
Unrealized gains | 1,329 | 767
Unrealized losses | 0 | 0
Estimated fair value | 105,070 | 83,915
State & Municipal [Member] |  |
Held-to-maturity securities, fair value to amortized cost [Abstract] |  |
Amortized cost | 234,300 | 243,133
Unrealized gains | 1,254 | 331
Unrealized losses | 360 | 1,616
Estimated fair value | $ 235,194 | $ 241,848

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- Definition This represents the amortized costs of securities available for sale and held to maturity that are pledged as collateral for securities sold under repurchase agreements. + References No definition available. + Details
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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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