Investments - Writedowns for Other-than-Temporary Impairments (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Than Temporary Impairment Losses Recognized [Line Items]
Writedowns for Other-Than-Temporary Impairments, Net Income, After tax	$ 0	$ 0	$ 3,640
Writedowns for Other-Than-Temporary Impairments, Other Comprehensive Income, After tax	0	0	0
Corporate Bonds [Member]
Other Than Temporary Impairment Losses Recognized [Line Items]
Writedowns for Other-Than-Temporary Impairments, Net Income, Pre-tax	0	0	5,600
Writedowns for Other-Than-Temporary Impairments, Other Comprehensive Income, Pre-tax	$ 0	$ 0	$ 0

After-tax 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.

No definition available.

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- Definition

Temporary impairment losses investments portion recognized in other comprehensive income loss before tax.

+ References

No definition available.

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- Definition

Temporary impairment losses investments portion recognized in other comprehensive income loss net of tax.

+ References

No definition available.

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- 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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 8B

-URI http://asc.fasb.org/extlink&oid=27724398&loc=SL6284393-111563

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