XML 66 R41.htm IDEA: XBRL DOCUMENT v2.4.1.9

Indebtedness (Details) (Point sixty three Percent Borrowing From Federal Home Loan Bank [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Point sixty three Percent Borrowing From Federal Home Loan Bank [Member]
Debt Instrument [Line Items]
FHLBI Borrowing	$ 15us-gaap_DebtInstrumentFaceAmount / us-gaap_DebtInstrumentAxis = sigi_PointsixtythreePercentBorrowingFromFederalHomeLoanBankMember

X

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration