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Fair Value Measurements (Carrying Value and Estimated Fair Value of Financial Instruments) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fixed maturity securities held to maturity at carry value	$ 1,070,578	$ 1,214,324
Fixed maturity securities, AFS	2,525,237	2,342,742
Equity securities, AFS	136,577	69,636
Short-term investments	142,809	161,155
Notes payable	262,346	262,333
Carrying Amount [Member]
Fixed maturity securities held to maturity at carry value	1,070,578	1,214,324
Fixed maturity securities, AFS	2,525,237	2,342,742
Equity securities, AFS	136,577	69,636
Short-term investments	142,809	161,155
Receivable for proceeds related to sale of Selective HR Solutions ("Selective HR")	4,531	5,002
Notes payable	262,346	262,333
Carrying Amount [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Notes payable	49,906	49,904
Carrying Amount [Member] | Six Point Seventy Percent Senior Notes [Member]
Notes payable	99,440	99,429
Carrying Amount [Member] | Seven Point Fifty Percent Junior Notes [Member]
Notes payable	100,000	100,000
Carrying Amount [Member] | Two Point Ninety Percent Borrowings from FHLBI [Member]
Notes payable	13,000	13,000
Fair Value [Member]
Fixed maturity securities held to maturity at carry value	1,120,977	1,256,294
Fixed maturity securities, AFS	2,525,237	2,342,742
Equity securities, AFS	136,577	69,636
Short-term investments	142,809	161,155
Receivable for proceeds related to sale of Selective HR Solutions ("Selective HR")	4,531	5,002
Notes payable	267,969	258,516
Fair Value [Member] | Seven Point Twenty Five Percent Senior Notes [Member]
Notes payable	55,699	55,190
Fair Value [Member] | Six Point Seventy Percent Senior Notes [Member]
Notes payable	98,250	90,097
Fair Value [Member] | Seven Point Fifty Percent Junior Notes [Member]
Notes payable	100,400	99,840
Fair Value [Member] | Two Point Ninety Percent Borrowings from FHLBI [Member]
Notes payable	$ 13,620	$ 13,389

X

- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity; such investments are measured at carrying value, which represents amortized cost adjusted for net unrealized gains (losses) resulting from: (i) an other-than-temporary impairment; or (ii) a previous available-for-sale designation. The held-to-maturity category is for those securities that the Entity has the positive intent and ability to hold until maturity.

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X

- Definition

The estimated proceeds associated with the sale of a subsidiary, net of payments received.

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- Definition

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading. Such securities are reported at fair value; unrealized gains and losses of such securities are excluded from earnings and included in other comprehensive income, a separate component of shareholders' equity, unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13, 137

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22

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- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading. Equity securities represent ownership interests or the right to acquire ownership interests in corporations and other legal entities which ownership interest is represented by shares of common or preferred stock (which is not mandatorily redeemable or redeemable at the option of the holder), convertible securities, stock rights, or stock warrants. Unrealized gains and losses related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale Security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain or loss of an Available-for-sale Security that is designated as being hedged in a fair value hedge shall be recognized in earnings during the period of the hedge, as should other than temporary declines in fair value below costs basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 19

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 86-40

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 3
-Subparagraph c

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- Definition

Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 20, 22
-Article 5

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- Definition

Other investments not otherwise specified in the taxonomy that will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher OTS
-Name Federal Regulation (FR)
-Number Title 12
-Chapter V
-Section 563c.102
-Subsection I

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph g
-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 5
-Article 9

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