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Fair Value Measurements (Changes in Fair Value of Securities Using Level 3 Inputs) (Details) (USD $) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2013 | Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | $ 42,277,000 |  | $ 27,910,000 |
Total net (losses) gains for the period included in OCI | 4,034,000 | [1] | 1,089,000 | [2]
Total net (losses) gains for the period included in net income | (1,389,000) | [3],[4] | 0 | [5],[6]
Purchases | 0 |  | 12,911,000 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | (2,089,000) |  | (3,742,000) |
Transfers into Level 3 | 0 |  | 12,642,000 |
Transfers out of Level 3 | (5,642,000) |  | (8,533,000) |
Fair value, Ending balance | 37,191,000 |  | 42,277,000 |
Estimated receivable amount related to sale of subsidiary | 1,000,000 |  |  |
Increase Decrease Of Receivable Related To Sale Of Subsidiary If Retention Assumption Were To Change |  |  | 100,000 |
Equity Securities [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 3,607,000 |  | 0 |
Total net (losses) gains for the period included in OCI | 3,935,000 | [1] | 0 | [2]
Total net (losses) gains for the period included in net income | 0 | [3],[4] | 0 | [5],[6]
Purchases | 0 |  | 0 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | 0 |  | 0 |
Transfers into Level 3 | 0 |  | 3,607,000 |
Transfers out of Level 3 | (4,642,000) |  | 0 |
Fair value, Ending balance | 2,900,000 |  | 3,607,000 |
AFS Fixed Maturity Securities [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Ending balance | 34,300,000 |  | 36,000,000 |
AFS Fixed Maturity Securities [Member] | U.S. Government and Government Agencies [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 19,789,000 |  | 21,741,000 |
Total net (losses) gains for the period included in OCI | (153,000) | [1] | (22,000) | [2]
Total net (losses) gains for the period included in net income | (43,000) | [3],[4] | (193,000) | [5],[6]
Purchases | 0 |  | 0 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | (621,000) |  | (1,737,000) |
Transfers into Level 3 | 0 |  | 0 |
Transfers out of Level 3 | 0 |  | 0 |
Fair value, Ending balance | 18,972,000 |  | 19,789,000 |
AFS Fixed Maturity Securities [Member] | Corporate Securities [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 2,946,000 |  | 2,603,000 |
Total net (losses) gains for the period included in OCI | 16,000 | [1] | 185,000 | [2]
Total net (losses) gains for the period included in net income | 0 | [3],[4] | 0 | [5],[6]
Purchases | 0 |  | 0 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | (60,000) |  | (630,000) |
Transfers into Level 3 | 0 |  | 788,000 |
Transfers out of Level 3 | 0 |  | 0 |
Fair value, Ending balance | 2,902,000 |  | 2,946,000 |
AFS Fixed Maturity Securities [Member] | Asset-backed Securities [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 6,068,000 |  | 0 |
Total net (losses) gains for the period included in OCI | (12,000) | [1] | 68,000 | [2]
Total net (losses) gains for the period included in net income | 0 | [3],[4] | 0 | [5],[6]
Purchases | 0 |  | 7,300,000 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | 0 |  | 0 |
Transfers into Level 3 | 0 |  | 0 |
Transfers out of Level 3 | 0 |  | (1,300,000) |
Fair value, Ending balance | 6,056,000 |  | 6,068,000 |
AFS Fixed Maturity Securities [Member] | Commercial Mortgage-backed Securities ("CMBS") [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 7,162,000 |  | 354,000 |
Total net (losses) gains for the period included in OCI | 248,000 | [1] | 858,000 | [2]
Total net (losses) gains for the period included in net income | 134,000 | [3],[4] | (51,000) | [5],[6]
Purchases | 0 |  | 5,611,000 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | (1,183,000) |  | (624,000) |
Transfers into Level 3 | 0 |  | 8,247,000 |
Transfers out of Level 3 | 0 |  | (7,233,000) |
Fair value, Ending balance | 6,361,000 |  | 7,162,000 |
Receivable For Proceeds From Divestiture Of Business [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Fair value, Beginning balance | 2,705,000 |  | 3,212,000 |
Total net (losses) gains for the period included in OCI | 0 | [1] | 0 | [2]
Total net (losses) gains for the period included in net income | (1,480,000) | [3],[4] | 244,000 | [5],[6]
Purchases | 0 |  | 0 |
Sales | 0 |  | 0 |
Issuances | 0 |  | 0 |
Settlements | (225,000) |  | (751,000) |
Transfers into Level 3 | 0 |  | 0 |
Transfers out of Level 3 | (1,000,000) |  | 0 |
Fair value, Ending balance | 0 |  | 2,705,000 |
Fair Value, Inputs, Level 3 [Member] | AFS Fixed Maturity Securities [Member] |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Transfers into Level 3 |  |  | $ 9,000,000 |
[1] | Amounts are reported in “Unrealized holding gains arising during period” on the Consolidated Statements of Comprehensive Income.
[2] | Amounts are reported in “Unrealized holding gains arising during period” on the Consolidated Statements of Comprehensive Income in our 2012 Annual Report.
[3] | Amounts are reported in “Net realized gains ” for realized gains and “Net investment income earned” for amortization of securities on the Consolidated Statements of Income.
[4] | For the receivable related to the sale of Selective HR, amounts in “Loss on disposal of discontinued operations, net of tax” relate to an impairment charge and amounts in “Other income” relate to interest accretion on the Consolidated Statements of Income.
[5] | Amounts are reported in “Net realized gains (losses)” for realized gains and losses and “Net investment income earned” for amortization for the CMBS securities on the Consolidated Statements of Income in our 2012 Annual Report.
[6] | Amounts are reported in “Other income” for the receivable related to the sale of Selective HR on the Consolidated Statements of Income in our 2012 Annual Report and are related to interest accretion on the receivable.

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- Definition The increase (decrease) of the receivable related to sale of subsidiary if retention of business assumption were to change by +/- 10%. + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3). + 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 (c)(1) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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- Definition This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances. + 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 (c) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -Subparagraph c -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. + Details
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