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Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015
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Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | $ 3,502,880 | $ 3,303,156
Fair value | 3,547,560 | 3,380,642
Amounts in the balance sheet | 3,547,560 | 3,380,642
Fixed Maturity Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 2,795,410 | 2,804,275
Fair value | 2,814,553 | 2,880,003
Amounts in the balance sheet | 2,814,554 | 2,880,003
Fixed Maturity Securities [Member] | U.S. Government Bonds And Agencies [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 12,288 | 22,542
Fair value | 12,275 | 22,507
Amounts in the balance sheet | 12,275 | 22,507
Fixed Maturity Securities [Member] | Municipal Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 2,432,181 | 2,417,046
Fair value | 2,449,292 | 2,505,039
Amounts in the balance sheet | 2,449,292 | 2,505,039
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 39,082 | 49,639
Fair value | 39,777 | 49,839
Amounts in the balance sheet | 39,778 | 49,839
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 189,780 | 255,606
Fair value | 189,688 | 243,372
Amounts in the balance sheet | 189,688 | 243,372
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 85,429 | 50,710
Fair value | 86,525 | 50,548
Amounts in the balance sheet | 86,525 | 50,548
Fixed Maturity Securities [Member] | Other asset-backed securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 36,650 | 8,732
Fair value | 36,996 | 8,698
Amounts in the balance sheet | 36,996 | 8,698
Equity Securities [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 331,770 | 313,528
Fair value | 357,327 | 315,362
Amounts in the balance sheet | 357,326 | 315,362
Equity Securities [Member] | Common Stock [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 286,503 | 275,479
Fair value | 316,450 | 280,263
Amounts in the balance sheet | 316,449 | 280,263
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 32,436 | 25,161
Fair value | 31,809 | 24,668
Amounts in the balance sheet | 31,809 | 24,668
Equity Securities [Member] | Private Credit Fund [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 12,831 | 12,888
Fair value | 9,068 | 10,431
Amounts in the balance sheet | 9,068 | 10,431
Short-term Investments [Member] |  |
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items] |  |
Cost | 375,700 | 185,353
Fair value | 375,680 | 185,277
Amounts in the balance sheet | $ 375,680 | $ 185,277

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- Definition This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611379-123010 + Details
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- Definition This item represents the original cost of the entity's investments including investments in equity securities and, as to fixed maturities, original cost reduced by repayments and adjusted for amortization of premiums or accrual of discounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611379-123010 + Details
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- Definition This item represents the reported amount of the entity's investments measured at fair value. Fair value is the price that would be received to sell an investment in an orderly transaction between market participants at the balance sheet [measurement] date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611379-123010 + Details
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