Investments - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014 Issue
Investment [Line Items]
Total issues of fixed-maturities and equities	1,589		1,604
Additional Other Than Temporary Impairment [Member]
Investment [Line Items]
Other-than-temporary impairments	$ 0	$ 0

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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 35

-Paragraph 34

-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25351-111560

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration