Summary of Cumulative Amounts Related to Credit Loss Portion of Other-Than-Temporary Impairment Losses on Debt Securities (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Beginning Balance	$ 2,361	$ 2,361	$ 2,361
Additions for Credit Loss Impairments recognized in the current period on securities not previously impaired	0	0	150
Additions for Credit Loss Impairments recognized in the current period on securities previously impaired	0	0	0
Reductions for Credit Loss Impairments previously recognized on securities sold during the period	(17)	0	(150)
Ending Balance	$ 2,344	$ 2,361	$ 2,361

No definition available.

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- Definition

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

+ References

+ Details

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- Definition

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which no such other than temporary impairment (OTTI) was previously recognized.

+ References

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- Definition

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=SL6284393-111563

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=SL6284393-111563

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- Definition

This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security because of the sale of impaired securities during the period.

+ References

+ Details

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