XML 35 R104.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Retirement Plans (Retirement Savings Plan) (Details) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Minimum Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 2.00% |  |
Maximum Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 50.00% |  |
Retirement Savings Plan [Member] |  |  |
Employer contribution | $ 7.0 | $ 6.3 | $ 6.0
Parent's common stock issued under this plan |  |  | 13,983
Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution To Retirement Savings Plan Percentage |  | 65.00% |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  | 7.00% |
Vesting Period Of Employer Contribution |  | 6 |
Enhanced Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution To Retirement Savings Plan Percentage |  | 100.00% |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage |  | 2.00% |
Non Elective Employer Contribution [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 4.00% | 2.00% |
Vesting Period Of Employer Contribution |  | 3 |
First Tier Of Employee Contributions [Member] | Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution To Retirement Savings Plan Percentage | 100.00% |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 3.00% |  |
Second Tier Of Employee Contributions [Member] | Employer Match [Member] | Retirement Savings Plan [Member] |  |  |
Maximum Employer Match Of Employee Contribution To Retirement Savings Plan Percentage | 50.00% |  |
Maximum Employer Match Of Employee Contribution Of Defined Compensation To Retirement Savings Plan Percentage | 3.00% |  |

X
- Definition Maximum percentage of defined compensation that an employee can contribute to the Retirement Savings Plan. + References No definition available. + Details
Name: | sigi_MaximumEmployeeContributionOfDefinedCompensationToRetirementSavingsPlanPercentage
Namespace Prefix: | sigi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Maximum percentage of an employee's contribution to the Retirement Savings Plan that the employer will match. + References No definition available. + Details
Name: | sigi_MaximumEmployerMatchOfEmployeeContributionOfDefinedCompensationToRetirementSavingsPlanPercentage
Namespace Prefix: | sigi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of an employee's contribution to the Retirement Savings Plan that the employer will match. + References No definition available. + Details
Name: | sigi_MaximumEmployerMatchOfEmployeeContributionToRetirementSavingsPlanPercentage
Namespace Prefix: | sigi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Minimum percentage of defined compensation that an employee can contribute to the Retirement Savings Plan. + References No definition available. + Details
Name: | sigi_MinimumEmployeeContributionOfDefinedCompensationToRetirementSavingsPlanPercentage
Namespace Prefix: | sigi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The period of time over which an employee is required to provide service in exchange for the employer match of the Retirement Savings Plan. + References No definition available. + Details
Name: | sigi_VestingPeriodOfEmployerContribution
Namespace Prefix: | sigi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of shares issued during the period to an employee benefit plan, such as a defined contribution or defined benefit plan. + References No definition available. + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesEmployeeBenefitPlan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration