Investments, Gain (Loss) on Investments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Gain (Loss) on Investments [Line Items]
Change in net unrealized appreciation (depreciation)	$ (78,546)	$ 31,662	$ (71,308)
Gross realized gains, gross realized losses and impairment losses [Abstract]
Gross realized gains	213,827	158,659	119,325
Gross realized losses	(16,108)	(15,229)	(16,278)
Impairment losses	(2,310)	(715)	(9,644)
Net realized gains (losses) on securities	195,409	142,715	93,403
Loss from joint ventures	0	0	(466)
Total net realized gains (losses)	195,409	142,715	92,937
Available-for-sale Securities [Member]
Gain (Loss) on Investments [Line Items]
Net realized investment gains (losses) and OTTI on investments	195,409	142,715	92,937
Available-for-sale Securities [Member] \| Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Net realized investment gains (losses) and OTTI on investments	195,652	142,284	93,017
Change in net unrealized appreciation (depreciation)	(78,604)	31,576	(71,304)
Available-for-sale Securities [Member] \| Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Net realized investment gains (losses) and OTTI on investments	487	330	151
Change in net unrealized appreciation (depreciation)	58	86	(4)
Available-for-sale Securities [Member] \| Joint Ventures [Member]
Gain (Loss) on Investments [Line Items]
Net realized investment gains (losses) and OTTI on investments	0	0	(466)
Available-for-sale Securities [Member] \| Other [Member]
Gain (Loss) on Investments [Line Items]
Net realized investment gains (losses) and OTTI on investments	(730)	101	235
Change in net unrealized appreciation (depreciation)	$ 0	$ 0	$ 0

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The difference between the carrying value of the note receivable from Sherman and proceeds received on repayment.

+ References

No definition available.

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- Definition

This item represents the pretax change in net unrealized holding gain (loss) on available-for-sale securities that has been included in accumulated other comprehensive income, a separate component of shareholders' equity, during the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 21

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

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- Definition

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-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.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

-Paragraph 9

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- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities and excluding other than temporary impairments (OTTI), if any, recognized elsewhere.

+ References

No definition available.

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- Definition

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-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.

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-Publisher FASB

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- Definition

This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity and any gains or losses realized during the period from the sale of investments accounted for under the cost method of accounting and/or investments that are separately or otherwise not categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

+ References

No definition available.

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- Definition

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.3(a))

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 3

-Subparagraph a

-Article 7

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