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Securities, Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Securities [Abstract] |  |
Percentage of total investment with unrealized losses | 90.50% | 69.50%
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months | $ 224,947 | $ 241,239
12 months or more | 304,984 | 173,642
Total | 529,931 | 414,881
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months | (3,486) | (2,004)
12 months or more | (10,915) | (5,054)
Total | (14,401) | (7,058)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months | 221,461 | 239,235
12 months or more | 294,069 | 168,588
Total | 515,530 | 407,823
U.S. Treasury and Government Agencies [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months | 132,224 | 136,688
12 months or more | 113,929 | 23,885
Total | 246,153 | 160,573
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months | (1,300) | (840)
12 months or more | (2,054) | (332)
Total | (3,354) | (1,172)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months | 130,924 | 135,848
12 months or more | 111,875 | 23,553
Total | 242,799 | 159,401
State and Political Subdivisions [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months | 59,535 | 34,283
12 months or more | 29,021 | 16,930
Total | 88,556 | 51,213
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months | (1,511) | (416)
12 months or more | (2,400) | (745)
Total | (3,911) | (1,161)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months | 58,024 | 33,867
12 months or more | 26,621 | 16,185
Total | 84,645 | 50,052
U.S. Government Sponsored Agency Mortgage-backed Securities [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months | 32,681 | 62,768
12 months or more | 162,034 | 117,827
Total | 194,715 | 180,595
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months | (674) | (643)
12 months or more | (6,461) | (3,364)
Total | (7,135) | (4,007)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months | 32,007 | 62,125
12 months or more | 155,573 | 114,463
Total | 187,580 | 176,588
Other Debt Securities [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months | 507 |
12 months or more | 0 |
Total | 507 |
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months | (1) |
12 months or more | 0 |
Total | (1) |
Available-for-sale, fair value [Abstract] |  |
Less than 12 months | 506 |
12 months or more | 0 |
Total | $ 506 |
Debt Securities [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months |  | 233,739
12 months or more |  | 158,642
Total |  | 392,381
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months |  | (1,899)
12 months or more |  | (4,441)
Total |  | (6,340)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months |  | 231,840
12 months or more |  | 154,201
Total |  | 386,041
CRA Investments Funds [Member] |  |
Available-for-sale, amortized cost [Abstract] |  |
Less than 12 months |  | 7,500
12 months or more |  | 15,000
Total |  | 22,500
Available-for-sale, gross unrealized losses [Abstract] |  |
Less than 12 months |  | (105)
12 months or more |  | (613)
Total |  | (718)
Available-for-sale, fair value [Abstract] |  |
Less than 12 months |  | 7,395
12 months or more |  | 14,387
Total |  | $ 21,782

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- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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