Components of Other-Than-Temporary Impairments Reflected in Statements of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
OTTI Losses on Securities	$ 1,892	$ 216	$ 4,554
Net OTTI Loss Recognized in OCI	1,813		3,572
Net OTTI Losses Recognized in Income	79	216	982
Gross OTTI losses
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
OTTI Losses on Securities	1,892	251	4,554
Net OTTI Loss Recognized in OCI	1,813		3,572
Net OTTI Losses Recognized in Income	79	251	982
Value of business acquired amortization
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
OTTI Losses on Securities		(35)
Net OTTI Losses Recognized in Income		$ (35)

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

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

-Publisher FASB

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

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-Name Accounting Standards Codification

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+ Details

- Definition

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

+ References+ 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.

+ References+ Details