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Investment Securities - Unrealized Loss Positions (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
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Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | $ 6,396 | $ 3,078
Greater than or equal to 12 continuous months | 103,910 | 127,053
Total Securities in a loss position | 110,306 | 130,131
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | (52) | (12)
Greater than or equal to 12 continuous months | (1,839) | (3,510)
Held-to-maturity, Gross Unrealized Losses | (1,891) | (3,522)
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 21,013 | 81,533
Available-for-sale, greater than 12 continuous months, Fair value | 218,008 | 234,850
Available-for-sale, Total Securities in a loss position, Fair Value | 239,021 | 316,383
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | (134) | (657)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (2,639) | (4,537)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (2,773) | (5,194)
Marketable Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Marketable securities, less than 12 continuous months, Fair value | 27,409 | 84,611
Marketable securities, greater than 12 continuous months, Fair value | 321,918 | 361,903
Marketable securities, Total Securities in a loss position, Fair value | 349,327 | 446,514
Marketable Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Marketable securities, less than 12 continuous months, Unrealized loss | (186) | (669)
Marketable securities, greater than 12 continuous months, Unrealized loss | (4,478) | (8,047)
Marketable securities, Total Securities in a loss position, Unrealized loss | (4,664) | (8,716)
MBS pass-through securities issued by FHLMC and FNMA |  |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | 2,663 | 198
Greater than or equal to 12 continuous months | 70,078 | 83,990
Total Securities in a loss position | 72,741 | 84,188
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | (39) | (9)
Greater than or equal to 12 continuous months | (1,534) | (2,800)
Held-to-maturity, Gross Unrealized Losses | (1,573) | (2,809)
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 0 | 19,971
Available-for-sale, greater than 12 continuous months, Fair value | 51,734 | 50,077
Available-for-sale, Total Securities in a loss position, Fair Value | 51,734 | 70,048
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | 0 | (128)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (560) | (1,102)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (560) | (1,230)
SBA-backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 12,253 | 13,175
Available-for-sale, greater than 12 continuous months, Fair value | 14,799 | 20,123
Available-for-sale, Total Securities in a loss position, Fair Value | 27,052 | 33,298
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | (123) | (122)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (102) | (284)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (225) | (406)
CMOs issued by FNMA |  |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | 0 | 0
Greater than or equal to 12 continuous months | 11,165 | 11,327
Total Securities in a loss position | 11,165 | 11,327
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | 0 | 0
Greater than or equal to 12 continuous months | (1) | (120)
Held-to-maturity, Gross Unrealized Losses | (1) | (120)
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 0 | 2,345
Available-for-sale, greater than 12 continuous months, Fair value | 17,786 | 16,138
Available-for-sale, Total Securities in a loss position, Fair Value | 17,786 | 18,483
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | 0 | (8)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (282) | (322)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (282) | (330)
CMOs issued by FHLMC |  |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | 0 | 2,880
Greater than or equal to 12 continuous months | 19,113 | 28,171
Total Securities in a loss position | 19,113 | 31,051
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | 0 | (3)
Greater than or equal to 12 continuous months | (292) | (567)
Held-to-maturity, Gross Unrealized Losses | (292) | (570)
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 4,187 | 24,094
Available-for-sale, greater than 12 continuous months, Fair value | 72,861 | 74,243
Available-for-sale, Total Securities in a loss position, Fair Value | 77,048 | 98,337
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | (3) | (330)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (789) | (1,267)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (792) | (1,597)
CMOs issued by GNMA |  |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | 3,733 |
Greater than or equal to 12 continuous months | 0 |
Total Securities in a loss position | 3,733 |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | (13) |
Greater than or equal to 12 continuous months | 0 |
Held-to-maturity, Gross Unrealized Losses | (13) |
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 3,529 | 1,666
Available-for-sale, greater than 12 continuous months, Fair value | 10,127 | 9,112
Available-for-sale, Total Securities in a loss position, Fair Value | 13,656 | 10,778
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | (4) | (7)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (298) | (267)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (302) | (274)
Debentures of government- sponsored agencies |  |
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 0 | 4,992
Available-for-sale, greater than 12 continuous months, Fair value | 11,385 | 11,349
Available-for-sale, Total Securities in a loss position, Fair Value | 11,385 | 16,341
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | 0 | (8)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (83) | (115)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (83) | (123)
Obligations of state and political subdivisions |  |
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Less than 12 continuous months | 0 | 0
Greater than or equal to 12 continuous months | 3,554 | 3,565
Total Securities in a loss position | 3,554 | 3,565
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Less than 12 continuous months | 0 | 0
Greater than or equal to 12 continuous months | (12) | (23)
Held-to-maturity, Gross Unrealized Losses | (12) | (23)
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 1,044 | 15,290
Available-for-sale, greater than 12 continuous months, Fair value | 38,308 | 52,804
Available-for-sale, Total Securities in a loss position, Fair Value | 39,352 | 68,094
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | (4) | (54)
Available-for-sale, greater than 12 continuous months, Unrealized loss | (520) | (1,166)
Available-for-sale, Total Securities in a loss position, Unrealized loss | (524) | (1,220)
Corporate bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available-for-sale, less than 12 continuous months, Fair value | 0 | 0
Available-for-sale, greater than 12 continuous months, Fair value | 1,008 | 1,004
Available-for-sale, Total Securities in a loss position, Fair Value | 1,008 | 1,004
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available-for-sale, less than 12 continuous months, Unrealized loss | 0 | 0
Available-for-sale, greater than 12 continuous months, Unrealized loss | (5) | (14)
Available-for-sale, Total Securities in a loss position, Unrealized loss | $ (5) | $ (14)

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