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Investments (Fair Value and Gross Pre-Tax Net Unrealized Unrecognized Loss of Securities By Length of Time) (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016
--- | --- | ---
AFS Fair Value, Less than 12 months |  | $ 467,158 | $ 1,358,111
AFS Unrealized Losses, Less than 12 months | [1] | (3,701) | (15,651)
AFS Fair Value, 12 months or longer |  | 7,533 | 15,626
AFS Unrealized Losses, 12 months or longer | [1] | (97) | (406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 474,691 | 1,373,737
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (3,798) | (16,057)
AFS Fixed Income Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 445,240 | 1,340,672
AFS Unrealized Losses, Less than 12 months | [1] | (2,341) | (14,991)
AFS Fair Value, 12 months or longer |  | 7,533 | 15,626
AFS Unrealized Losses, 12 months or longer | [1] | (97) | (406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 452,773 | 1,356,298
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (2,438) | (15,397)
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 19,058 | 6,419
AFS Unrealized Losses, Less than 12 months | [1] | (136) | (36)
AFS Fair Value, 12 months or longer |  | 250 | 0
AFS Unrealized Losses, 12 months or longer | [1] | (1) | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 19,308 | 6,419
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (137) | (36)
AFS Fixed Income Securities [Member] | Foreign Government [Member] |  |  |
AFS Fair Value, Less than 12 months |  |  | 13,075
AFS Unrealized Losses, Less than 12 months | [1] |  | (16)
AFS Fair Value, 12 months or longer |  |  | 0
AFS Unrealized Losses, 12 months or longer | [1] |  | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  |  | 13,075
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] |  | (16)
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 67,538 | 306,509
AFS Unrealized Losses, Less than 12 months | [1] | (432) | (5,304)
AFS Fair Value, 12 months or longer |  | 0 | 0
AFS Unrealized Losses, 12 months or longer | [1] | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 67,538 | 306,509
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (432) | (5,304)
AFS Fixed Income Securities [Member] | Corporate Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 108,011 | 462,902
AFS Unrealized Losses, Less than 12 months | [1] | (827) | (5,771)
AFS Fair Value, 12 months or longer |  | 1,475 | 4,913
AFS Unrealized Losses, 12 months or longer | [1] | (18) | (89)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 109,486 | 467,815
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (845) | (5,860)
AFS Fixed Income Securities [Member] | Collateralized Loan Obligations and Other Asset Backed Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 88,636 | 189,795
AFS Unrealized Losses, Less than 12 months | [1] | (143) | (354)
AFS Fair Value, 12 months or longer |  | 0 | 319
AFS Unrealized Losses, 12 months or longer | [1] | 0 | (1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 88,636 | 190,114
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (143) | (355)
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 65,016 | 82,492
AFS Unrealized Losses, Less than 12 months | [1] | (245) | (1,021)
AFS Fair Value, 12 months or longer |  | 5,216 | 1,645
AFS Unrealized Losses, 12 months or longer | [1] | (73) | (7)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 70,232 | 84,137
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (318) | (1,028)
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 96,981 | 279,480
AFS Unrealized Losses, Less than 12 months | [1] | (558) | (2,489)
AFS Fair Value, 12 months or longer |  | 592 | 8,749
AFS Unrealized Losses, 12 months or longer | [1] | (5) | (309)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 97,573 | 288,229
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (563) | (2,798)
Equity Securities [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 21,918 | 17,439
AFS Unrealized Losses, Less than 12 months | [1] | (1,360) | (660)
AFS Fair Value, 12 months or longer |  | 0 | 0
AFS Unrealized Losses, 12 months or longer | [1] | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 21,918 | 17,439
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (1,360) | (660)
Equity Securities [Member] | Common Stock [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 18,032 | 11,271
AFS Unrealized Losses, Less than 12 months | [1] | (1,342) | (305)
AFS Fair Value, 12 months or longer |  | 0 | 0
AFS Unrealized Losses, 12 months or longer | [1] | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 18,032 | 11,271
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | (1,342) | (305)
Equity Securities [Member] | Preferred Stock [Member] |  |  |
AFS Fair Value, Less than 12 months |  | 3,886 | 6,168
AFS Unrealized Losses, Less than 12 months | [1] | (18) | (355)
AFS Fair Value, 12 months or longer |  | 0 | 0
AFS Unrealized Losses, 12 months or longer | [1] | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value |  | 3,886 | 6,168
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [1] | $ (18) | $ (355)
[1] | Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI.

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