XML 110 R82.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Reserve for Losses and Loss Expenses (Roll Forward of Gross and Net Asbestos and Net Environmental Incurred Losses and Loss Expenses and Related Reserves) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Salvage and Subrogation Recoveries, Value | $ 64,900 | $ 62,100 | $ 65,100
Reserves for losses and loss expenses at beginning of year, gross | 30,411 | 30,653 | 32,764
Incurred losses and loss expenses, gross | 1,483 | 2,968 | 167
Less: losses and loss expenses paid, gross | (1,932) | (3,210) | (2,278)
Reserves for losses and loss expenses at the end of year, gross | 29,962 | 30,411 | 30,653
Reserves for losses and loss expenses at beginning of year, net | 23,161 | 22,994 | 25,167
Incurred losses and loss expenses, net | 1,380 | 3,320 | 0
Less: losses and loss expenses paid, net | (1,825) | (3,153) | (2,173)
Reserves for losses and loss expenses at the end of year, net | 22,716 | 23,161 | 22,994
Asbestos [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Reserves for losses and loss expenses at beginning of year, gross | 8,024 | 8,751 | 8,897
Incurred losses and loss expenses, gross | 77 | (428) | 60
Less: losses and loss expenses paid, gross | (254) | (299) | (206)
Reserves for losses and loss expenses at the end of year, gross | 7,847 | 8,024 | 8,751
Reserves for losses and loss expenses at beginning of year, net | 6,793 | 7,314 | 7,518
Incurred losses and loss expenses, net | 77 | (77) | 0
Less: losses and loss expenses paid, net | (255) | (444) | (204)
Reserves for losses and loss expenses at the end of year, net | 6,615 | 6,793 | 7,314
Enviromental [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Reserves for losses and loss expenses at beginning of year, gross | 22,387 | 21,902 | 23,867
Incurred losses and loss expenses, gross | 1,406 | 3,396 | 107
Less: losses and loss expenses paid, gross | (1,678) | (2,911) | (2,072)
Reserves for losses and loss expenses at the end of year, gross | 22,115 | 22,387 | 21,902
Reserves for losses and loss expenses at beginning of year, net | 16,368 | 15,680 | 17,649
Incurred losses and loss expenses, net | 1,303 | 3,397 | 0
Less: losses and loss expenses paid, net | (1,570) | (2,709) | (1,969)
Reserves for losses and loss expenses at the end of year, net | $ 16,101 | $ 16,368 | $ 15,680

X
- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, before estimated recoveries from reinsurers. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before effects of reinsurance, of expense for claims incurred and costs incurred in the claim settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGrossIncurredLoss1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cash outflow to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsGrossPaymentForClaims
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after effects of reinsurance, of expense for claims incurred and costs incurred in the claim settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetIncurredLoss1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetPaymentForClaims
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpenseLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated amount as of the balance sheet date to be received by an insurer from the sale of property (usually damaged) on which the insurer has paid a total claim to the insured and has obtained title to the property and the right of an insurer to pursue any course of recovery of damages, in its name or in the name of the policyholder, against a third party who is liable for costs relating to an insured event that have been paid by the insurer. Estimated salvage and subrogation is generally deducted from the liability for unpaid claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 30 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6482241&loc=d3e13779-158432 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 30 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6482241&loc=d3e13783-158432 + Details
Name: | us-gaap_SalvageAndSubrogationRecoveriesValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | sigi_ScheduleOfLiabilityForUnpaidEnvironmentalClaimsAndClaimsAdjustmentExpenseAxis=us-gaap_AsbestosIssueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | sigi_ScheduleOfLiabilityForUnpaidEnvironmentalClaimsAndClaimsAdjustmentExpenseAxis=sigi_EnvironmentalclaimsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |