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Securities (Details 2) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2017 USD ($) security | Jun. 30, 2016 USD ($) | Jun. 30, 2017 USD ($) security | Jun. 30, 2016 USD ($) | Dec. 31, 2016 USD ($) security
Fair Value |  |  |  |  |
Less Than 12 Months | $ 1,661,833,000 |  | $ 1,661,833,000 |  | $ 2,162,896,000
12 Months or More | 301,499,000 |  | 301,499,000 |  | 253,038,000
Total | 1,963,332,000 |  | 1,963,332,000 |  | 2,415,934,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (31,297,000) |  | (31,297,000) |  | (51,760,000)
12 Months or More | (10,133,000) |  | (10,133,000) |  | (4,581,000)
Total | (41,430,000) |  | (41,430,000) |  | $ (56,341,000)
Impairment loss | $ 0 | $ 0 | $ 0 | $ 0 |
Number of securities in an unrealized loss position | security | 140 |  | 140 |  | 170
Fair Value |  |  |  |  |
Less Than 12 Months | $ 1,661,833,000 |  | $ 1,661,833,000 |  | $ 2,162,896,000
12 Months or More | 301,499,000 |  | 301,499,000 |  | 253,038,000
Total | 1,963,332,000 |  | 1,963,332,000 |  | 2,415,934,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (31,297,000) |  | (31,297,000) |  | (51,760,000)
12 Months or More | (10,133,000) |  | (10,133,000) |  | (4,581,000)
Total | (41,430,000) |  | (41,430,000) |  | (56,341,000)
U.S. Treasury securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 536,842,000 |  | 536,842,000 |  | 670,268,000
12 Months or More | 10,014,000 |  | 10,014,000 |  | 0
Total | 546,856,000 |  | 546,856,000 |  | 670,268,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (6,932,000) |  | (6,932,000) |  | (9,829,000)
12 Months or More | (6,000) |  | (6,000) |  | 0
Total | $ (6,938,000) |  | $ (6,938,000) |  | $ (9,829,000)
Number of securities in an unrealized loss position | security | 24 |  | 24 |  | 26
U.S. government agency and U.S. government sponsored enterprise debt securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | $ 134,583,000 |  | $ 134,583,000 |  | $ 203,901,000
12 Months or More | 0 |  | 0 |  | 0
Total | 134,583,000 |  | 134,583,000 |  | 203,901,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (2,655,000) |  | (2,655,000) |  | (3,249,000)
12 Months or More | 0 |  | 0 |  | 0
Total | $ (2,655,000) |  | $ (2,655,000) |  | $ (3,249,000)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities |  |  |  |  |
Gross Unrealized Losses |  |  |  |  |
Number of securities in an unrealized loss position | security | 74 |  | 74 |  | 82
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | $ 213,675,000 |  | $ 213,675,000 |  | $ 202,106,000
12 Months or More | 48,309,000 |  | 48,309,000 |  | 29,201,000
Total | 261,984,000 |  | 261,984,000 |  | 231,307,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (5,521,000) |  | (5,521,000) |  | (5,452,000)
12 Months or More | (1,215,000) |  | (1,215,000) |  | (766,000)
Total | (6,736,000) |  | (6,736,000) |  | (6,218,000)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 423,711,000 |  | 423,711,000 |  | 629,324,000
12 Months or More | 124,052,000 |  | 124,052,000 |  | 119,603,000
Total | 547,763,000 |  | 547,763,000 |  | 748,927,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (4,904,000) |  | (4,904,000) |  | (9,594,000)
12 Months or More | (2,553,000) |  | (2,553,000) |  | (1,955,000)
Total | (7,457,000) |  | (7,457,000) |  | (11,549,000)
Municipal securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 17,652,000 |  | 17,652,000 |  | 57,655,000
12 Months or More | 2,795,000 |  | 2,795,000 |  | 2,692,000
Total | 20,447,000 |  | 20,447,000 |  | 60,347,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (312,000) |  | (312,000) |  | (1,699,000)
12 Months or More | (92,000) |  | (92,000) |  | (201,000)
Total | $ (404,000) |  | $ (404,000) |  | (1,900,000)
Number of securities in an unrealized loss position | security | 13 |  | 13 |  |
Non-agency residential mortgage-backed securities | Investment grade |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | $ 4,742,000 |  | $ 4,742,000 |  | 5,033,000
12 Months or More | 0 |  | 0 |  | 6,444,000
Total | 4,742,000 |  | 4,742,000 |  | 11,477,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (66,000) |  | (66,000) |  | (101,000)
12 Months or More | 0 |  | 0 |  | (14,000)
Total | (66,000) |  | (66,000) |  | (115,000)
Corporate debt securities | Investment grade |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | 2,296,000 |  | 2,296,000 |  | 71,667,000
Total | 2,296,000 |  | 2,296,000 |  | 71,667,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | (176,000) |  | (176,000) |  | (375,000)
Total | (176,000) |  | (176,000) |  | (375,000)
Corporate debt securities | Non-investment grade |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | 9,492,000 |  | 9,492,000 |  | 9,173,000
Total | 9,492,000 |  | 9,492,000 |  | 9,173,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | (699,000) |  | (699,000) |  | (1,018,000)
Total | (699,000) |  | (699,000) |  | (1,018,000)
Foreign bonds | Investment grade |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 299,434,000 |  | 299,434,000 |  | 363,618,000
12 Months or More | 104,541,000 |  | 104,541,000 |  | 14,258,000
Total | 403,975,000 |  | 403,975,000 |  | 377,876,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (10,570,000) |  | (10,570,000) |  | (21,327,000)
12 Months or More | (5,392,000) |  | (5,392,000) |  | (252,000)
Total | $ (15,962,000) |  | $ (15,962,000) |  | $ (21,579,000)
Number of securities in an unrealized loss position | security | 13 |  | 13 |  | 13
Other securities |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | $ 31,194,000 |  | $ 31,194,000 |  | $ 30,991,000
12 Months or More | 0 |  | 0 |  | 0
Total | 31,194,000 |  | 31,194,000 |  | 30,991,000
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | (337,000) |  | (337,000) |  | (509,000)
12 Months or More | 0 |  | 0 |  | 0
Total | (337,000) |  | (337,000) |  | (509,000)
Non-agency commercial mortgage-backed security |  |  |  |  |
Fair Value |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | 0 |  | 0 |  | 0
Total | 0 |  | 0 |  | 0
Gross Unrealized Losses |  |  |  |  |
Less Than 12 Months | 0 |  | 0 |  | 0
12 Months or More | 0 |  | 0 |  | 0
Total | $ 0 |  | $ 0 |  | $ 0

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