XML 85 R58.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Investments (Held-To-Maturity Securities Disclosure) (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
Amortized Cost | $ 201,054 | $ 317,179
Net Unrealized Gains (Losses) | 300 | 958
Total HTM fixed income securities carrying value | 201,354 | 318,137
Unrecognized Holding Gains | 8,190 | 15,824
Unrecognized Holding Losses | 0 | 0
Total HTM fixed income securities fair value | $ 209,544 | 333,961
Held To Maturity Securities Average Duration | 1 year 6 months |
Foreign Government [Member] |  |
Amortized Cost |  | 5,292
Net Unrealized Gains (Losses) |  | 47
Total HTM fixed income securities carrying value |  | 5,339
Unrecognized Holding Gains |  | 55
Unrecognized Holding Losses |  | 0
Total HTM fixed income securities fair value |  | 5,394
Obligations of States and Political Subdivisions [Member] |  |
Amortized Cost | $ 175,269 | 285,301
Net Unrealized Gains (Losses) | 848 | 2,071
Total HTM fixed income securities carrying value | 176,117 | 287,372
Unrecognized Holding Gains | 5,763 | 11,760
Unrecognized Holding Losses | 0 | 0
Total HTM fixed income securities fair value | 181,880 | 299,132
Corporate Securities [Member] |  |
Amortized Cost | 20,228 | 18,899
Net Unrealized Gains (Losses) | (185) | (273)
Total HTM fixed income securities carrying value | 20,043 | 18,626
Unrecognized Holding Gains | 1,972 | 2,796
Unrecognized Holding Losses | 0 | 0
Total HTM fixed income securities fair value | 22,015 | 21,422
Asset-backed Securities [Member] |  |
Amortized Cost | 1,030 | 2,818
Net Unrealized Gains (Losses) | (120) | (455)
Total HTM fixed income securities carrying value | 910 | 2,363
Unrecognized Holding Gains | 118 | 460
Unrecognized Holding Losses | 0 | 0
Total HTM fixed income securities fair value | 1,028 | 2,823
Commercial Mortgage Backed Securities [Member] |  |
Amortized Cost | 4,527 | 4,869
Net Unrealized Gains (Losses) | (243) | (432)
Total HTM fixed income securities carrying value | 4,284 | 4,437
Unrecognized Holding Gains | 337 | 753
Unrecognized Holding Losses | 0 | 0
Total HTM fixed income securities fair value | $ 4,621 | $ 5,190

X
- Definition Held to maturity securities average duration. + References No definition available. + Details
Name: | sigi_HeldToMaturitySecuritiesAverageDuration
Namespace Prefix: | sigi_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The remaining aggregate increase (decrease) in the market value of held-to-maturity securities either (i) prior to the securities' transfer to a held-to-maturity designation or (ii) resulting from a non-credit other-than-temporary impairment. + References No definition available. + Details
Name: | sigi_HeldToMaturitySecuritiesNetUnrealizedGainsLosses
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.6) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_HeldToMaturitySecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity. + References No definition available. + Details
Name: | us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_DebtSecurityAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtSecurityAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |