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Investments (Tables) | 9 Months Ended
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Sep. 30, 2016
Investments [Line Items] |
Schedule of Held-to-maturity Securities |
September 30, 2016 |  |  |  |  |  |  |  |  |  |  |  |
($ in thousands) |  | Amortized Cost |  | Net Unrealized Gains (Losses) |  | Carrying Value |  | Unrecognized Holding Gains |  | Unrecognized Holding Losses |  | Fair Value
Obligations of states and political subdivisions |  | $ | 104,159 |  |  | 414 |  |  | 104,573 |  |  | 3,256 |  |  | — |  |  | 107,829 |
Corporate securities |  | 23,722 |  |  | (165 | ) |  | 23,557 |  |  | 2,294 |  |  | — |  |  | 25,851 |
Asset-backed securities (“ABS”) |  | 51 |  |  | — |  |  | 51 |  |  | — |  |  | — |  |  | 51 |
Commercial mortgage-backed securities (“CMBS”) |  | 2,346 |  |  | (55 | ) |  | 2,291 |  |  | 72 |  |  | — |  |  | 2,363 |
Total HTM fixed income securities |  | $ | 130,278 |  |  | 194 |  |  | 130,472 |  |  | 5,622 |  |  | — |  |  | 136,094 |
December 31, 2015 |  |  |  |  |  |  |  |  |  |  |  |
($ in thousands) |  | Amortized Cost |  | Net Unrealized Gains (Losses) |  | Carrying Value |  | Unrecognized Holding Gains |  | Unrecognized Holding Losses |  | Fair Value
Obligations of states and political subdivisions |  | $ | 175,269 |  |  | 848 |  |  | 176,117 |  |  | 5,763 |  |  | — |  |  | 181,880 |
Corporate securities |  | 20,228 |  |  | (185 | ) |  | 20,043 |  |  | 1,972 |  |  | — |  |  | 22,015 |
ABS |  | 1,030 |  |  | (120 | ) |  | 910 |  |  | 118 |  |  | — |  |  | 1,028 |
CMBS |  | 4,527 |  |  | (243 | ) |  | 4,284 |  |  | 337 |  |  | — |  |  | 4,621 |
Total HTM fixed income securities |  | $ | 201,054 |  |  | 300 |  |  | 201,354 |  |  | 8,190 |  |  | — |  |  | 209,544 |
Schedule of Available-for-sale Securities |
September 30, 2016 |  |  |  |  |  |  |  |
($ in thousands) |  | Cost/ Amortized Cost |  | Unrealized Gains |  | Unrealized Losses |  | Fair Value
AFS fixed income securities: |  |  |  |  |  |  |  |
U.S. government and government agencies |  | $ | 86,491 |  |  | 3,400 |  |  | — |  |  | 89,891 |
Foreign government |  | 9,041 |  |  | 443 |  |  | — |  |  | 9,484 |
Obligations of states and political subdivisions |  | 1,376,245 |  |  | 70,984 |  |  | (333 | ) |  | 1,446,896 |
Corporate securities |  | 2,136,761 |  |  | 60,784 |  |  | (1,427 | ) |  | 2,196,118 |
ABS |  | 282,558 |  |  | 1,964 |  |  | (69 | ) |  | 284,453 |
CMBS |  | 261,233 |  |  | 5,634 |  |  | (93 | ) |  | 266,774 |
Residential mortgage-backed securities (“RMBS”) |  | 529,938 |  |  | 9,294 |  |  | (316 | ) |  | 538,916 |
Total AFS fixed income securities |  | 4,682,267 |  |  | 152,503 |  |  | (2,238 | ) |  | 4,832,532 |
AFS equity securities: |  |  |  |  |  |  |  |
Common stock |  | 111,746 |  |  | 24,832 |  |  | (1,089 | ) |  | 135,489 |
Preferred stock |  | 11,235 |  |  | 580 |  |  | — |  |  | 11,815 |
Total AFS equity securities |  | 122,981 |  |  | 25,412 |  |  | (1,089 | ) |  | 147,304 |
Total AFS securities |  | $ | 4,805,248 |  |  | 177,915 |  |  | (3,327 | ) |  | 4,979,836 |
December 31, 2015 |  |  |  |  |  |  |  |
($ in thousands) |  | Cost/ Amortized Cost |  | Unrealized Gains |  | Unrealized Losses |  | Fair Value
AFS fixed income securities: |  |  |  |  |  |  |  |
U.S. government and government agencies |  | $ | 99,485 |  |  | 4,721 |  |  | (91 | ) |  | 104,115 |
Foreign government |  | 14,885 |  |  | 298 |  |  | (2 | ) |  | 15,181 |
Obligations of states and political subdivisions |  | 1,314,779 |  |  | 44,523 |  |  | (160 | ) |  | 1,359,142 |
Corporate securities |  | 1,892,296 |  |  | 23,407 |  |  | (15,521 | ) |  | 1,900,182 |
ABS |  | 244,541 |  |  | 531 |  |  | (918 | ) |  | 244,154 |
CMBS |  | 245,252 |  |  | 750 |  |  | (2,410 | ) |  | 243,592 |
RMBS |  | 541,276 |  |  | 4,274 |  |  | (3,713 | ) |  | 541,837 |
Total AFS fixed income securities |  | 4,352,514 |  |  | 78,504 |  |  | (22,815 | ) |  | 4,408,203 |
AFS equity securities: |  |  |  |  |  |  |  |
Common stock |  | 181,991 |  |  | 14,796 |  |  | (1,998 | ) |  | 194,789 |
Preferred stock |  | 11,825 |  |  | 477 |  |  | (40 | ) |  | 12,262 |
Total AFS equity securities |  | 193,816 |  |  | 15,273 |  |  | (2,038 | ) |  | 207,051 |
Total AFS securities |  | $ | 4,546,330 |  |  | 93,777 |  |  | (24,853 | ) |  | 4,615,254 |
Schedule of Fair Value and Gross Pre-Tax Net Unrealized/Unrecognized Loss of Securities by Length of Time |
September 30, 2016 |  | Less than 12 months |  | 12 months or longer
($ in thousands) |  | Fair Value |  | Unrealized Losses 1 |  | Fair Value |  | Unrealized Losses 1
AFS fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |
Obligations of states and political subdivisions |  | $ | 74,989 |  |  | (333 | ) |  | — |  |  | — |
Corporate securities |  | 155,880 |  |  | (1,139 | ) |  | 30,469 |  |  | (288 | )
ABS |  | 21,766 |  |  | (66 | ) |  | 2,450 |  |  | (3 | )
CMBS |  | 24,633 |  |  | (59 | ) |  | 8,709 |  |  | (34 | )
RMBS |  | 13,674 |  |  | (40 | ) |  | 37,677 |  |  | (276 | )
Total AFS fixed income securities |  | 290,942 |  |  | (1,637 | ) |  | 79,305 |  |  | (601 | )
AFS equity securities: |  |  |  |  |  |  |  |
Common stock |  | 12,528 |  |  | (1,089 | ) |  | — |  |  | — |
Total AFS equity securities |  | 12,528 |  |  | (1,089 | ) |  | — |  |  | — |
Total AFS |  | $ | 303,470 |  |  | (2,726 | ) |  | 79,305 |  |  | (601 | )
December 31, 2015 |  | Less than 12 months |  | 12 months or longer
($ in thousands) |  | Fair Value |  | Unrealized Losses 1 |  | Fair Value |  | Unrealized Losses 1
AFS fixed income securities: |  |  |  |  |  |  |  |  |  |  |  |
U.S. government and government agencies |  | $ | 16,006 |  |  | (87 | ) |  | 396 |  |  | (4 | )
Foreign government |  | 1,067 |  |  | (2 | ) |  | — |  |  | — |
Obligations of states and political subdivisions |  | 28,617 |  |  | (160 | ) |  | — |  |  | — |
Corporate securities |  | 761,479 |  |  | (12,671 | ) |  | 50,382 |  |  | (2,850 | )
ABS |  | 197,477 |  |  | (807 | ) |  | 12,022 |  |  | (111 | )
CMBS |  | 146,944 |  |  | (2,196 | ) |  | 15,385 |  |  | (214 | )
RMBS |  | 264,914 |  |  | (1,992 | ) |  | 63,395 |  |  | (1,721 | )
Total AFS fixed income securities |  | 1,416,504 |  |  | (17,915 | ) |  | 141,580 |  |  | (4,900 | )
AFS equity securities: |  |  |  |  |  |  |  |
Common stock |  | 31,148 |  |  | (1,998 | ) |  | — |  |  | — |
Preferred stock |  | 1,531 |  |  | (40 | ) |  | — |  |  | — |
Total AFS equity securities |  | 32,679 |  |  | (2,038 | ) |  | — |  |  | — |
Total AFS |  | $ | 1,449,183 |  |  | (19,953 | ) |  | 141,580 |  |  | (4,900 | )
1 Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI.
Schedule of The Number Of Securities In An Unrealized Unrecognized Loss Position |
($ in thousands) |  |
September 30, 2016 |  | December 31, 2015
Number of Issues | % of Market/Book | Unrealized Loss |  | Number of Issues | % of Market/Book | Unrealized/ Unrecognized Loss
180 |  | 80% - 99% | $ | 3,327 |  |  | 606 |  | 80% - 99% | $ | 22,971 |
— |  | 60% - 79% | — |  |  | 3 |  | 60% - 79% | 1,888 |
— |  | 40% - 59% | — |  |  | — |  | 40% - 59% | — |
— |  | 20% - 39% | — |  |  | — |  | 20% - 39% | — |
— |  | 0% - 19% | — |  |  | — |  | 0% - 19% | — |
|  |  | $ | 3,327 |  |  |  |  |  | $ | 24,859 |
Schedule of Other Investment Portfolio By Strategy And Remaining Commitment Amount and Maximum Exposure to Loss Associated With Each Strategy |
Other Investments |  | September 30, 2016 |  | December 31, 2015
($ in thousands) |  | Carrying Value |  | Remaining Commitment |  | Maximum Exposure to Loss 1 |  | Carrying Value |  | Remaining Commitment |  | Maximum Exposure to Loss 1
Alternative Investments |  |  |  |  |  |  |  |  |  |  |  |  |  |
Private equity |  | $ | 35,444 |  |  | 57,793 |  |  | 93,237 |  |  | 35,088 |  |  | 30,204 |  |  | 65,292 |
Private credit |  | 27,709 |  |  | 30,763 |  |  | 58,472 |  |  | 13,246 |  |  | 15,129 |  |  | 28,375 |
Real assets |  | 15,329 |  |  | 22,922 |  |  | 38,251 |  |  | 19,500 |  |  | 25,820 |  |  | 45,320 |
Total alternative investments |  | 78,482 |  |  | 111,478 |  |  | 189,960 |  |  | 67,834 |  |  | 71,153 |  |  | 138,987 |
Other securities |  | 10,030 |  |  | 22,611 |  |  | 32,641 |  |  | 10,008 |  |  | 3,200 |  |  | 13,208 |
Total other investments |  | $ | 88,512 |  |  | 134,089 |  |  | 222,601 |  |  | 77,842 |  |  | 74,353 |  |  | 152,195 |
1 The maximum exposure to loss includes both the carry value of these investments and the related unfunded commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant.
Schedule of Aggregated Summarized Income Statement Financial Information For Partnerships In Our Alternative Investment Portfolio |
Income Statement Information |  | Quarter ended June 30, |  | Nine months ended June 30,
($ in millions) |  | 2016 |  | 2015 |  | 2016 |  | 2015
Net investment (loss) income |  | $ | (55.4 | ) |  | 44.1 |  |  | 26.1 |  |  | 139.6 |
Realized gains |  | 245.6 |  |  | 385.2 |  |  | 1,186.8 |  |  | 977.7 |
Net change in unrealized depreciation |  | 117.8 |  |  | (222.2 | ) |  | (1,132.8 | ) |  | (1,089.0 | )
Net gain |  | $ | 308.0 |  |  | 207.1 |  |  | 80.1 |  |  | 28.3 |
Selective’s insurance subsidiaries’ other investments gain (loss) |  | $ | 1.6 |  |  | 1.3 |  |  | — |  |  | (0.8 | )
Schedule of Securities Pledged As Collateral |
($ in millions) |  | FHLBI Collateral |  | FHLBNY Collateral |  | State and Regulatory Deposits |  | Total
U.S. government and government agencies |  | $ | 7.4 |  |  | — |  |  | 23.1 |  |  | 30.5 |
CMBS |  | 1.0 |  |  | — |  |  | — |  |  | 1.0 |
RMBS |  | 53.1 |  |  | 64.4 |  |  | — |  |  | 117.5 |
Total pledged as collateral |  | $ | 61.5 |  |  | 64.4 |  |  | 23.1 |  |  | 149.0 |
Schedule of Net Investment Income Earned |
|  | Quarter ended September 30, |  | Nine Months ended September 30,
($ in thousands) |  | 2016 |  | 2015 |  | 2016 |  | 2015
Fixed income securities |  | $ | 32,453 |  |  | 30,601 |  |  | $ | 95,850 |  |  | 92,227 |
Equity securities |  | 1,506 |  |  | 2,370 |  |  | 5,940 |  |  | 6,546 |
Short-term investments |  | 192 |  |  | 24 |  |  | 493 |  |  | 72 |
Other investments |  | 1,628 |  |  | 1,337 |  |  | (49 | ) |  | (781 | )
Investment expenses |  | (2,404 | ) |  | (2,271 | ) |  | (6,908 | ) |  | (6,856 | )
Net investment income earned |  | $ | 33,375 |  |  | 32,061 |  |  | $ | 95,326 |  |  | 91,208 |
Schedule of OTTI By Asset Type |
Third Quarter 2016 |  | Gross |  | Included in Other Comprehensive Income ("OCI") |  | Recognized in Earnings
($ in thousands) |  |  |
AFS equity securities: |  |  |  |  |  |
Common stock |  | $ | 342 |  |  | — |  |  | 342 |
Total AFS equity securities |  | 342 |  |  | — |  |  | 342 |
Total OTTI losses |  | $ | 342 |  |  | — |  |  | 342 |
Third Quarter 2015 |  | Gross |  | Included in OCI |  | Recognized in Earnings
($ in thousands) |  |  |
AFS fixed income securities: |  |  |  |  |  |
Corporate securities |  | $ | 253 |  |  | — |  |  | 253 |
Total AFS fixed income securities |  | 253 |  |  | — |  |  | 253 |
AFS equity securities: |  |  |  |  |  |
Common stock |  | 1,029 |  |  | — |  |  | 1,029 |
Total AFS equity securities |  | 1,029 |  |  | — |  |  | 1,029 |
Total OTTI losses |  | $ | 1,282 |  |  | — |  |  | 1,282 |
Nine Months 2016 |  | Gross |  | Included in OCI |  | Recognized in Earnings
($ in thousands) |  |  |
AFS fixed income securities: |  |  |  |  |  |
Corporate securities |  | $ | 1,077 |  |  | — |  |  | 1,077 |
RMBS |  | 98 |  |  | 10 |  |  | 88 |
Total AFS fixed income securities |  | 1,175 |  |  | 10 |  |  | 1,165 |
AFS equity securities: |  |  |  |  |  |
Common stock |  | 3,316 |  |  | — |  |  | 3,316 |
Preferred stock |  | 3 |  |  | — |  |  | 3 |
Total AFS equity securities |  | 3,319 |  |  | — |  |  | 3,319 |
Total OTTI losses |  | $ | 4,494 |  |  | 10 |  |  | 4,484 |
Nine Months 2015 |  | Gross |  | Included in OCI |  | Recognized in Earnings
($ in thousands) |  |  |
AFS fixed income securities: |  |  |  |  |  |
Corporate securities |  | $ | 1,445 |  |  | — |  |  | 1,445 |
RMBS |  | 1 |  |  | — |  |  | 1 |
Total AFS fixed income securities |  | 1,446 |  |  | — |  |  | 1,446 |
AFS equity securities: |  |  |  |  |  |
Common stock |  | 6,201 |  |  | — |  |  | 6,201 |
Preferred stock |  | 180 |  |  | — |  |  | 180 |
Total AFS equity securities |  | 6,381 |  |  | — |  |  | 6,381 |
Total OTTI losses |  | $ | 7,827 |  |  | — |  |  | 7,827 |
Schedule of Components of Net Realized Gains Excluding OTTI Charges |
|  | Quarter ended September 30, |  | Nine Months ended September 30,
($ in thousands) |  | 2016 |  | 2015 |  | 2016 |  | 2015
HTM fixed income securities |  |  |  |  |  |  |  |
Gains |  | $ | — |  |  | 3 |  |  | 3 |  |  | 5 |
Losses |  | — |  |  | — |  |  | (1 | ) |  | (1 | )
AFS fixed income securities |  |  |  |  |  |  |  |  |  |  |  |
Gains |  | 2,204 |  |  | 169 |  |  | 3,189 |  |  | 2,158 |
Losses |  | (40 | ) |  | — |  |  | (81 | ) |  | (130 | )
AFS equity securities |  |  |  |  |  |  |  |  |  |  |  |
Gains |  | 1,863 |  |  | 1,419 |  |  | 4,364 |  |  | 23,567 |
Losses |  | — |  |  | (1 | ) |  | (240 | ) |  | (1,347 | )
Other investments |  |  |  |  |  |  |  |
Gains |  | 3 |  |  | — |  |  | 3 |  |  | — |
Losses |  | — |  |  | — |  |  | (4 | ) |  | (654 | )
Total net realized gains (excluding OTTI charges) |  | $ | 4,030 |  |  | 1,590 |  |  | 7,233 |  |  | 23,598 |
Held To Maturity Fixed Income Securities [Member] |
Investments [Line Items] |
Schedule of Fixed Maturity Securities By Contractual Maturities |
($ in thousands) |  | Carrying Value |  | Fair Value
Due in one year or less |  | $ | 59,074 |  |  | 59,671 |
Due after one year through five years |  | 62,778 |  |  | 66,622 |
Due after five years through 10 years |  | 8,620 |  |  | 9,801 |
Total HTM fixed income securities |  | $ | 130,472 |  |  | 136,094 |
AFS Fixed Income Securities [Member] |
Investments [Line Items] |
Schedule of Fixed Maturity Securities By Contractual Maturities |
($ in thousands) |  | Fair Value
Due in one year or less |  | $ | 491,206 |
Due after one year through five years |  | 2,403,246 |
Due after five years through 10 years |  | 1,823,028 |
Due after 10 years |  | 115,052 |
Total AFS fixed income securities |  | $ | 4,832,532 |

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- Definition Tabular disclosure of financial instruments held by the entity for its own account for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions. Description may include equity, fixed income, debt or other securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728 + Details
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