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Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) $ in Thousands | Sep. 30, 2018 USD ($) security | Dec. 31, 2017 USD ($) security
--- | --- | ---
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 277 | 91
Fair Value, Less than 12 Months | $ 733,743 | $ 190,832
Unrealized Losses, Less than 12 Months | $ (12,538) | $ (2,234)
Number of positions, 12 Months or More | security | 113 | 94
Fair value, 12 Months or More | $ 233,707 | $ 183,115
Unrealized Losses, 12 Months or More | $ (14,445) | $ (8,254)
Number of positions | security | 390 | 185
Fair value | $ 967,450 | $ 373,947
Unrealized Losses | $ (26,983) | $ (10,488)
Obligations of other U.S. Government agencies and corporations |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 1 | 1
Fair Value, Less than 12 Months | $ 490 | $ 497
Unrealized Losses, Less than 12 Months | $ (10) | $ (3)
Number of positions, 12 Months or More | security | 2 | 2
Fair value, 12 Months or More | $ 1,982 | $ 1,999
Unrealized Losses, 12 Months or More | $ (38) | $ (27)
Number of positions | security | 3 | 3
Fair value | $ 2,472 | $ 2,496
Unrealized Losses | $ (48) | $ (30)
Obligations of states and political subdivisions |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 79 | 23
Fair Value, Less than 12 Months | $ 52,161 | $ 11,860
Unrealized Losses, Less than 12 Months | $ (758) | $ (59)
Number of positions, 12 Months or More | security | 12 | 12
Fair value, 12 Months or More | $ 7,432 | $ 7,728
Unrealized Losses, 12 Months or More | $ (435) | $ (210)
Number of positions | security | 91 | 35
Fair value | $ 59,593 | $ 19,588
Unrealized Losses | $ (1,193) | $ (269)
Trust preferred securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 0 | 0
Fair Value, Less than 12 Months | $ 0 | $ 0
Unrealized Losses, Less than 12 Months | $ 0 | $ 0
Number of positions, 12 Months or More | security | 2 | 2
Fair value, 12 Months or More | $ 10,304 | $ 9,388
Unrealized Losses, 12 Months or More | $ (2,047) | $ (3,054)
Number of positions | security | 2 | 2
Fair value | $ 10,304 | $ 9,388
Unrealized Losses | $ (2,047) | $ (3,054)
Other debt securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 14 | 2
Fair Value, Less than 12 Months | $ 13,823 | $ 756
Unrealized Losses, Less than 12 Months | $ (208) | $ (12)
Number of positions, 12 Months or More | security | 3 | 2
Fair value, 12 Months or More | $ 6,020 | $ 6,308
Unrealized Losses, 12 Months or More | $ (239) | $ (64)
Number of positions | security | 17 | 4
Fair value | $ 19,843 | $ 7,064
Unrealized Losses | $ (447) | $ (76)
Government agency mortgage backed securities | Residential mortgage backed securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 119 | 29
Fair Value, Less than 12 Months | $ 440,200 | $ 64,595
Unrealized Losses, Less than 12 Months | $ (7,536) | $ (659)
Number of positions, 12 Months or More | security | 52 | 44
Fair value, 12 Months or More | $ 94,329 | $ 89,414
Unrealized Losses, 12 Months or More | $ (5,353) | $ (2,400)
Number of positions | security | 171 | 73
Fair value | $ 534,529 | $ 154,009
Unrealized Losses | $ (12,889) | $ (3,059)
Government agency mortgage backed securities | Commercial mortgage-backed securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 8 | 2
Fair Value, Less than 12 Months | $ 11,396 | $ 5,629
Unrealized Losses, Less than 12 Months | $ (188) | $ (17)
Number of positions, 12 Months or More | security | 2 | 3
Fair value, 12 Months or More | $ 5,072 | $ 5,872
Unrealized Losses, 12 Months or More | $ (374) | $ (217)
Number of positions | security | 10 | 5
Fair value | $ 16,468 | $ 11,501
Unrealized Losses | $ (562) | $ (234)
Government agency collateralized mortgage obligations | Residential mortgage backed securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 51 | 33
Fair Value, Less than 12 Months | $ 186,677 | $ 102,509
Unrealized Losses, Less than 12 Months | $ (3,468) | $ (1,470)
Number of positions, 12 Months or More | security | 40 | 29
Fair value, 12 Months or More | $ 108,568 | $ 62,406
Unrealized Losses, 12 Months or More | $ (5,959) | $ (2,282)
Number of positions | security | 91 | 62
Fair value | $ 295,245 | $ 164,915
Unrealized Losses | $ (9,427) | $ (3,752)
Government agency collateralized mortgage obligations | Commercial mortgage-backed securities |  |
Available for Sale: |  |
Number of positions, Less than 12 Months | security | 5 | 1
Fair Value, Less than 12 Months | $ 28,996 | $ 4,986
Unrealized Losses, Less than 12 Months | $ (370) | $ (14)
Number of positions, 12 Months or More | security | 0 | 0
Fair value, 12 Months or More | $ 0 | $ 0
Unrealized Losses, 12 Months or More | $ 0 | $ 0
Number of positions | security | 5 | 1
Fair value | $ 28,996 | $ 4,986
Unrealized Losses | $ (370) | $ (14)

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