XML 37 R31.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Investments (Available-For-Sale Securities Disclosure) (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | $ 3,958,250,000 |  | $ 3,831,327,000 |
Unrealized Gains | 156,602,000 |  | 128,951,000 |
Unrealized Losses | (13,304,000) |  | (51,971,000) |
Total AFS securities | 4,101,548,000 |  | 3,908,307,000 |
AFS Fixed Income Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 3,792,036,000 |  | 3,675,977,000 |
Unrealized Gains | 111,465,000 |  | 91,434,000 |
Unrealized Losses | (13,301,000) |  | (51,875,000) |
Total AFS securities | 3,890,200,000 |  | 3,715,536,000 |
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 149,537,000 |  | 163,218,000 |
Unrealized Gains | 9,474,000 |  | 10,661,000 |
Unrealized Losses | (202,000) |  | (504,000) |
Total AFS securities | 158,809,000 |  | 173,375,000 |
AFS Fixed Income Securities [Member] | Foreign Government [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 27,046,000 |  | 29,781,000 |
Unrealized Gains | 983,000 |  | 906,000 |
Unrealized Losses | (1,000) |  | (72,000) |
Total AFS securities | 28,028,000 |  | 30,615,000 |
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 1,080,039,000 |  | 946,455,000 |
Unrealized Gains | 30,696,000 |  | 25,194,000 |
Unrealized Losses | (3,681,000) |  | (20,025,000) |
Total AFS securities | 1,107,054,000 |  | 951,624,000 |
AFS Fixed Income Securities [Member] | Corporate Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 1,730,192,000 |  | 1,707,928,000 |
Unrealized Gains | 56,587,000 |  | 44,004,000 |
Unrealized Losses | (4,186,000) |  | (17,049,000) |
Total AFS securities | 1,782,593,000 |  | 1,734,883,000 |
AFS Fixed Income Securities [Member] | Asset-Backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 131,434,000 |  | 140,430,000 |
Unrealized Gains | 945,000 |  | 934,000 |
Unrealized Losses | (210,000) |  | (468,000) |
Total AFS securities | 132,169,000 |  | 140,896,000 |
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 170,298,000 | [1] | 172,288,000 | [1]
Unrealized Gains | 3,246,000 | [1] | 2,462,000 | [1]
Unrealized Losses | (1,073,000) | [1] | (3,466,000) | [1]
Total AFS securities | 172,471,000 | [1] | 171,284,000 | [1]
Government guaranteed agency securities fair value | 23,700,000 |  | 30,000,000 |
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 503,490,000 | [2] | 515,877,000 | [2]
Unrealized Gains | 9,534,000 | [2] | 7,273,000 | [2]
Unrealized Losses | (3,948,000) | [2] | (10,291,000) | [2]
Total AFS securities | 509,076,000 | [2] | 512,859,000 | [2]
Government guaranteed agency securities fair value | 41,800,000 |  | 55,200,000 |
Equity Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 166,214,000 |  | 155,350,000 |
Unrealized Gains | 45,137,000 |  | 37,517,000 |
Unrealized Losses | (3,000) |  | (96,000) |
Total AFS securities | $ 211,348,000 |  | $ 192,771,000 |
[1] | CMBS includes government guaranteed agency securities with a fair value of $23.7 million at June 30, 2014 and $30.0 million at December 31, 2013.
[2] | RMBS includes government guaranteed agency securities with a fair value of $41.8 million at June 30, 2014 and $55.2 million at December 31, 2013.

X
- Definition Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities. + References No definition available. + Details
Name: | sigi_AFSSecuritiesGrossUnrealizedGain
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale equity securities. + References No definition available. + Details
Name: | sigi_AFSSecuritiesGrossUnrealizedLosses
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value of agency securities that are issued by a particular agency of the federal government which are guaranteed by the U.S. government. + References No definition available. + Details
Name: | sigi_GovernmentGuaranteedAgencySecuritiesFairValue
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration