XML 94 R65.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Investments (Number of Securities in an Unrealized Unrecognized Loss Position) (Details) (USD $) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2013 Securities | Dec. 31, 2012 Securities
Number of securities in an unrealized/unrecognized loss position | 557 | 101
Unrealized Unrecognized Loss | $ 52,011,000 | $ 2,934,000
Unrealized Unrecognized Losses Period Increase Decrease | 49,100,000 |
Securities In Unrealized Unrecognized Loss Position For More Than Twelve Months | 2,900,000 | 1,700,000
Eighty Percent to Ninety-Nine Percent [Member] |  |
Number of securities in an unrealized/unrecognized loss position | 556 | 100
Unrealized Unrecognized Loss | 51,835,000 | 2,701,000
Sixty Percent to Seventy-Nine Percent [Member] |  |
Number of securities in an unrealized/unrecognized loss position | 1 | 1
Unrealized Unrecognized Loss | 176,000 | 233,000
Forty Percent to Fifty-Nine Percent [Member] |  |
Number of securities in an unrealized/unrecognized loss position | 0 | 0
Unrealized Unrecognized Loss | 0 | 0
Twenty Percent to Thirty-Nine Percent [Member] |  |
Number of securities in an unrealized/unrecognized loss position | 0 | 0
Unrealized Unrecognized Loss | 0 | 0
Zero Percent to Nineteen Percent [Member] |  |
Number of securities in an unrealized/unrecognized loss position | 0 | 0
Unrealized Unrecognized Loss | $ 0 | $ 0
10 Year U.S. Treasury Note [Member] |  |
Increase of Yield on Note | 127 |

X
- Definition Increase (decrease) in basis points of the stated interest rate on the debt instrument. + References No definition available. + Details
Name: | sigi_DebtInstrumentsInterestRateIncreaseDecrease
Namespace Prefix: | sigi_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition This item contains disclosure of the number of available-for-sale and held-to-maturity securities determined to be in an unrealized/unrecognized loss position. + References No definition available. + Details
Name: | sigi_NumberOfSecuritiesInUnrealizedUnrecognizedLossPosition
Namespace Prefix: | sigi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents total unrealized and unrecognized losses of all available-for-sale and held-to-maturity securities in an unrealized and unrecognized loss position for more than 12 months as of the end of the period. + References No definition available. + Details
Name: | sigi_SecuritiesInUnrealizedUnrecognizedLossPositionForMoreThanTwelveMonthsUnrealizedUnrecognizedLoss
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the sum of (i) the excess of amortized cost over fair value for available-for-sale securities that are in a loss position and (ii) the market fluctuations on held-to-maturity securities from the later of (a) the date a security is designated as held-to-maturity; or (b) the date that an other-than-temporary impairment charge is recognized on a held-to-maturity security for securities that are in an unrecognized loss position. + References No definition available. + Details
Name: | sigi_UnrealizedUnrecognizedLoss
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the increase or decrease in unrealized/unrecognized losses for available-for-sale and held-to-maturities securities. + References No definition available. + Details
Name: | sigi_UnrealizedUnrecognizedLossesPeriodIncreaseDecrease
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration