Summary Of Activity Related to OTTI Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2011 Investment	Sep. 30, 2012 Investment	Sep. 30, 2011 Investment
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities	10	4	16
Total other-than-temporary impairment losses	$ 1,241	$ 693	$ 2,338
Portion of loss recognized in other comprehensive income (before tax)	618	43	941
Net other-than-temporary impairment losses recognized in earnings	623	650	1,397
Residential Mortgage Backed Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities	10	1	15
Total other-than-temporary impairment losses	1,241	54	1,791
Portion of loss recognized in other comprehensive income (before tax)	618	43	941
Net other-than-temporary impairment losses recognized in earnings	623	11	850
Equity Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Number of Securities		3	1
Total other-than-temporary impairment losses		639	547
Net other-than-temporary impairment losses recognized in earnings		$ 639	$ 547

The amount by which the fair value of an investment 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.

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-Publisher FASB

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-2/124-2

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+ Details

- Definition

Before tax amount of other than temporary impairment (OTTI) on a debt security, categorized as either available-for-sale or held-to-maturity, recognized in other comprehensive income (loss).

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 16B

-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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 130

-Paragraph 17

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-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 7

-Footnote 2

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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-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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+ Details

- Definition

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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