XML 74 R47.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Retirement Plans (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |
Schedule Of Plan Terms In Effect And Revisions Of Retirement Savings Plan | (a) Selective Insurance Retirement Savings Plan (“Retirement Savings Plan”) SICA offers a voluntary defined contribution 401(k) plan, which is available to most of our employees and is a tax-qualified retirement plan subject to the Employee Retirement Income Security Act of 1974 ("ERISA"). Expense recorded for this plan was $15.8 million in 2017, $15.0 million in 2016, and $14.1 million in 2015.
Schedule of Funded Status Of Retirement Income Plan And Retirement Life Plan |
December 31, |  | Pension Plan
($ in thousands) |  | 2017 |  | 2016
Change in Benefit Obligation: |  |  |  |  |  |
Benefit obligation, beginning of year |  | $ | 330,588 |  |  | 310,308 |
Service cost |  | — |  |  | 1,647 |
Interest cost |  | 12,490 |  |  | 12,336 |
Actuarial losses |  | 31,158 |  |  | 15,086 |
Benefits paid |  | (9,825 | ) |  | (8,789 | )
Benefit obligation, end of year |  | $ | 364,411 |  |  | 330,588 |
Change in Fair Value of Assets: |  |  |  |  |  |
Fair value of assets, beginning of year |  | $ | 316,515 |  |  | 249,700 |
Actual return on plan assets, net of expenses |  | 46,983 |  |  | 21,079 |
Contributions by the employer to funded plans |  | 10,000 |  |  | 54,525 |
Benefits paid |  | (9,825 | ) |  | (8,789 | )
Fair value of assets, end of year |  | $ | 363,673 |  |  | 316,515 |
Funded status |  | $ | (738 | ) |  | (14,073 | )
Schedule of Amounts Recognized in Consolidated Balance Sheet |
Amounts Recognized in the Consolidated Balance Sheet: |  |  |  |  |  |
Liabilities |  | $ | (738 | ) |  | (14,073 | )
Net pension liability, end of year |  | $ | (738 | ) |  | (14,073 | )
Schedule of Amounts recognized in Accumulated Other than Comprehensive Income |
Amounts Recognized in AOCI: |  |  |  |  |  |
Net actuarial loss |  | $ | 87,438 |  |  | 85,845 |
Total |  | $ | 87,438 |  |  | 85,845 |
Schedule of Other Information as of December 31 |
Other Information as of December 31: |  |  |  |  |  |
Accumulated benefit obligation |  | $ | 364,411 |  |  | 330,588 |
Schedule of Components Of Net Periodic Benefit Cost And Other Amounts Recognized In Other Comprehensive Income |
|  | Pension Plan
($ in thousands) |  | 2017 |  | 2016 |  | 2015
Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income: |  |  |  |  |  |  |  |  |
Net Periodic Benefit Cost: |  |  |  |  |  |  |  |  |
Service cost |  | $ | — |  |  | 1,647 |  |  | 7,215 |
Interest cost |  | 12,490 |  |  | 12,336 |  |  | 13,668 |
Expected return on plan assets |  | (19,419 | ) |  | (17,309 | ) |  | (15,969 | )
Amortization of unrecognized actuarial loss |  | 2,001 |  |  | 6,299 |  |  | 6,831 |
Total net periodic cost |  | $ | (4,928 | ) |  | 2,973 |  |  | 11,745 |
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income: |  |  |  |  |  |  |  |  |
Net actuarial loss (gain) |  | $ | 3,594 |  |  | 11,316 |  |  | (1,425 | )
Reversal of amortization of net actuarial loss |  | (2,001 | ) |  | (6,299 | ) |  | (6,831 | )
Total recognized in other comprehensive income |  | $ | 1,593 |  |  | 5,017 |  |  | (8,256 | )
Total recognized in net periodic benefit cost and other comprehensive income |  | $ | (3,335 | ) |  | 7,990 |  |  | 3,489 |
Schedule Of Weighted- Average Expense and Liability Assumptions |
|  | Pension Plan
|  | 2017 |  | 2016 |  | 2015
Weighted-Average Expense Assumptions for the years ended December 31: |  |  |  |  |  |  |
Discount rate |  | 4.41 | % |  | 4.69 |  | 4.29
Expected return on plan assets |  | 6.24 |  |  | 6.37 |  | 6.27
Rate of compensation increase 1 |  | — |  |  | — |  | 4.00
Weighted-Average Liability Assumptions as of December 31: |  |  |  |  |
Discount rate |  | 3.78 | % |  | 4.41
Schedule of Allocation of Plan Assets |
|  | 2017 |  | 2016
|  | Target Percentage 2 |  | Actual Percentage |  | Actual Percentage
Return seeking assets 1 |  | 20% - 60% |  |  | 58 | % |  | 50 | %
Liability hedging assets |  | 40% - 80% |  |  | 42 | % |  | 50 | %
Total |  | 100 | % |  | 100 | % |  | 100 | %
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value |
December 31, 2017 |  |  |  | Fair Value Measurements Using
($ in thousands) |  | Assets Measured at Fair Value |  | Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1)1 |  | Significant Other Observable Inputs (Level 2)1 |  | Significant Unobservable Inputs (Level 3)
Description |  |  |  |  |  |  |  |  |  |  |  |
Measured on a recurring basis: |  |  |  |  |  |  |  |  |  |  |  |
AFS fixed income securities: |  |  |  |  |  |  |  |
U.S. government and government agencies |  | $ | 49,740 |  |  | 24,652 |  |  | 25,088 |  |  | — |
Foreign government |  | 18,555 |  |  | — |  |  | 18,555 |  |  | — |
Obligations of states and political subdivisions |  | 1,582,970 |  |  | — |  |  | 1,582,970 |  |  | — |
Corporate securities |  | 1,617,468 |  |  | — |  |  | 1,617,468 |  |  | — |
CLO and other ABS |  | 795,458 |  |  | — |  |  | 795,458 |  |  | — |
CMBS |  | 383,449 |  |  | — |  |  | 376,895 |  |  | 6,554 |
RMBS |  | 714,882 |  |  | — |  |  | 714,882 |  |  | — |
Total AFS fixed income securities |  | 5,162,522 |  |  | 24,652 |  |  | 5,131,316 |  |  | 6,554 |
AFS equity securities: |  |  |  |  |  |  |  |
Common stock 2 |  | 167,757 |  |  | 138,640 |  |  | — |  |  | 5,398 |
Preferred stock |  | 14,948 |  |  | 14,948 |  |  | — |  |  | — |
Total AFS equity securities |  | 182,705 |  |  | 153,588 |  |  | — |  |  | 5,398 |
Total AFS securities |  | 5,345,227 |  |  | 178,240 |  |  | 5,131,316 |  |  | 11,952 |
Short-term investments |  | 165,555 |  |  | 165,555 |  |  | — |  |  | — |
Total assets measured at fair value |  | $ | 5,510,782 |  |  | 343,795 |  |  | 5,131,316 |  |  | 11,952 |
December 31, 2016 |  |  |  | Fair Value Measurements Using
($ in thousands) |  | Assets Measured at Fair Value |  | Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1)1 |  | Significant Other Observable Inputs (Level 2)1 |  | Significant Unobservable Inputs (Level 3)
Description |  |  |  |  |  |  |  |  |  |  |  |
Measured on a recurring basis: |  |  |  |  |  |  |  |  |  |  |  |
AFS fixed income securities: |  |  |  |  |  |  |  |
U.S. government and government agencies |  | $ | 77,333 |  |  | 27,520 |  |  | 49,813 |  |  | — |
Foreign government |  | 26,865 |  |  | — |  |  | 26,865 |  |  | — |
Obligations of states and political subdivisions |  | 1,379,593 |  |  | — |  |  | 1,379,593 |  |  | — |
Corporate securities |  | 1,997,753 |  |  | — |  |  | 1,997,753 |  |  | — |
CLO and other ABS |  | 528,960 |  |  | — |  |  | 528,960 |  |  | — |
CMBS |  | 256,842 |  |  | — |  |  | 256,842 |  |  | — |
RMBS |  | 525,194 |  |  | — |  |  | 525,194 |  |  | — |
Total AFS fixed income securities |  | 4,792,540 |  |  | 27,520 |  |  | 4,765,020 |  |  | — |
AFS equity securities: |  |  |  |  |  |  |  |
Common stock |  | 130,608 |  |  | 122,932 |  |  | — |  |  | 7,676 |
Preferred stock |  | 16,145 |  |  | 16,145 |  |  | — |  |  | — |
Total AFS equity securities |  | 146,753 |  |  | 139,077 |  |  | — |  |  | 7,676 |
Total AFS securities |  | 4,939,293 |  |  | 166,597 |  |  | 4,765,020 |  |  | 7,676 |
Short-term investments |  | 221,701 |  |  | 221,701 |  |  | — |  |  | — |
Total assets measured at fair value |  | $ | 5,160,994 |  |  | 388,298 |  |  | 4,765,020 |  |  | 7,676 |
1 There were no transfers of securities between Level 1 and Level 2. 2 In accordance with ASU 2015-07, investments amounting to $23.7 million at December 31, 2017, respectively, were measured at fair value using the net asset value per share (or its practical expedient) and have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total assets measured at fair value.
Schedule of Expected Benefit Payments | Payments
($ in thousands) |  | Pension Plan
Benefits Expected to be Paid in Future |  |  |
Fiscal Years: |  |  |
2018 |  | $ | 12,913 |
2019 |  | 12,936 |
2020 |  | 13,987 |
2021 |  | 15,093 |
2022 |  | 16,128 |
2023-2027 |  | 94,542 |
Retirement Income Plan [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Schedule of Quantitative Disclosures of our Financial Assets that were Measured at Fair Value |
December 31, 2017 |  |  |  | Fair Value Measurements at 12/31/17 Using
($ in thousands) |  | Assets Measured at Fair Value At 12/31/17 |  | Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) |  | Significant Other Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3)
Description |  |  |  |  |  |  |  |  |  |  |  |
Return seeking assets: |  |  |  |  |  |  |  |
Long-duration fixed income: |  |  |  |  |  |  |  |  |  |  |  |
Global asset allocation fund |  | $ | 41,309 |  |  | 41,309 |  |  | — |  |  | — |
Global equity: |  |  |  |  |  |  |  |
Non-U.S. equity |  | 67,989 |  |  | 67,989 |  |  | — |  |  | — |
U.S. equity |  | 66,353 |  |  | 66,353 |  |  | — |  |  | — |
Total global equity |  | 134,342 |  |  | 134,342 |  |  | — |  |  | — |
Private assets: |  |  |  |  |  |  |  |  |
Limited partnerships (at net asset value)1: |  |  |  |  |  |  |  |
Real assets |  | 16,305 |  |  | — |  |  | — |  |  | — |
Private equity |  | 1,096 |  |  | — |  |  | — |  |  | — |
Private credit |  | 460 |  |  | — |  |  | — |  |  | — |
Hedge fund |  | 15,192 |  |  | — |  |  | — |  |  | — |
Total limited partnerships |  | 33,053 |  |  | — |  |  | — |  |  | — |
Other private assets |  | 980 |  |  | — |  |  | — |  |  | 980 |
Total private assets |  | 34,033 |  |  | — |  |  | — |  |  | 980 |
Total return seeking assets |  | 209,684 |  |  | 175,651 |  |  | — |  |  | 980 |
Liability hedging assets: |  |  |  |  |  |  |  |
Long-duration fixed income: |  |  |  |  |  |  |  |
Extended duration fixed income |  | 146,837 |  |  | 146,837 |  |  | — |  |  | — |
Cash and short-term investments: |  |  |  |  |  |  |  |
Short-term investments |  | 4,939 |  |  | 4,939 |  |  | — |  |  | — |
Deposit administration contracts |  | 1,615 |  |  | — |  |  | 1,615 |  |  | — |
Total cash and short-term investments |  | 6,554 |  |  | 4,939 |  |  | 1,615 |  |  | — |
Total liability hedging assets |  | 153,391 |  |  | 151,776 |  |  | 1,615 |  |  | — |
Total invested assets |  | $ | 363,075 |  |  | $ | 327,427 |  |  | $ | 1,615 |  |  | $ | 980 |
December 31, 2016 |  |  |  | Fair Value Measurements at 12/31/16 Using
($ in thousands) |  | Assets Measured at Fair Value At 12/31/16 |  | Quoted Prices in Active Markets for Identical Assets/ Liabilities (Level 1) |  | Significant Other Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3)
Description |  |  |  |  |  |  |  |  |  |  |  |
Return seeking assets: |  |  |  |  |  |  |  |
Long-duration fixed income: |  |  |  |  |  |  |  |  |  |  |  |
Global asset allocation fund |  | $ | 37,878 |  |  | 37,878 |  |  | — |  |  | — |
Global equity: |  |  |  |  |  |  |  |
Non-U.S. equity |  | 48,836 |  |  | 48,836 |  |  | — |  |  | — |
U.S. equity |  | 55,073 |  |  | 55,073 |  |  | — |  |  | — |
Total global equity |  | 103,909 |  |  | 103,909 |  |  | — |  |  | — |
Private assets (limited partnerships, at net asset value)1: |  |  |  |  |  |  |  |  |
Real assets |  | 15,466 |  |  | — |  |  | — |  |  | — |
Private equity |  | 1,615 |  |  | — |  |  | — |  |  | — |
Private credit |  | 1,108 |  |  | — |  |  | — |  |  | — |
Total private assets |  | 18,189 |  |  | — |  |  | — |  |  | — |
Total return seeking assets |  | 159,976 |  |  | 141,787 |  |  | — |  |  | — |
Liability hedging assets: |  |  |  |  |  |  |  |
Long-duration fixed income: |  |  |  |  |  |  |  |
Extended duration fixed income |  | 131,457 |  |  | 131,457 |  |  | — |  |  | — |
Cash and short-term investments: |  |  |  |  |  |  |  |
Short-term investments |  | 23,722 |  |  | 23,722 |  |  | — |  |  | — |
Deposit administration contracts |  | 1,832 |  |  | — |  |  | 1,832 |  |  | — |
Total cash and short-term investments |  | 25,554 |  |  | 23,722 |  |  | 1,832 |  |  | — |
Total liability hedging assets |  | 157,011 |  |  | 155,179 |  |  | 1,832 |  |  | — |
Total invested assets |  | $ | 316,987 |  |  | $ | 296,966 |  |  | $ | 1,832 |  |  | $ | — |
1 In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value per share (or its practical expedient) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to total Pension Plan invested assets.

X
- Definition Tabular disclosure regarding the terms and revisions of the Retirement Savings Plan + References No definition available. + Details
Name: | sigi_ScheduleOfPlanTermsInEffectAndRevisionsOfRetirementSavingsPlanTableTextBlock
Namespace Prefix: | sigi_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the change in the benefit obligation, fair value of plan assets, and funded status of pension plans or other employee benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(b)(c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ChangesInProjectedBenefitObligationsFairValueOfPlanAssetsAndFundedStatusOfPlanTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of assets measured at fair value measured on a recurring or nonrecurring basis. Includes, but is not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19190-110258 + Details
Name: | us-gaap_FairValueAssetsMeasuredOnRecurringAndNonrecurringBasisTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefit obligations including accumulated benefit obligation and projected benefit obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAccumulatedAndProjectedBenefitObligationsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAllocationOfPlanAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amounts that are recognized in the balance sheet (or statement of financial position) for pension plans and/or other employee benefit plans, showing separately the assets and current and noncurrent liabilities (if applicable) recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAmountsRecognizedInBalanceSheetTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the assumptions used to determine for pension plans and/or other employee benefit plans the benefit obligation and net benefit cost, including assumed discount rates, rate increase in compensation increase, and expected long-term rates of return on plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfAssumptionsUsedTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfExpectedBenefitPaymentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetBenefitCostsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amounts related to pension plans and/or other employee benefit plans in accumulated other comprehensive income or loss that have not yet been recognized as components of net periodic benefit cost, such as the net gain (loss), net prior service cost or credit, and net transition asset or obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
Name: | us-gaap_ScheduleOfNetPeriodicBenefitCostNotYetRecognizedTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |