Fair Value Measurements - Summary of Carrying Values and Corresponding Fair Values for Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held to maturity	$ 664,371	$ 561,179
Fixed maturity securities-held-to-maturity	639,631us-gaap_HeldToMaturitySecurities	536,583us-gaap_HeldToMaturitySecurities
Fixed maturity securities-available for sale	331,242	237,877
Equity securities	28	9,302
Short-term investments	33,684us-gaap_ShortTermInvestments	84,422us-gaap_ShortTermInvestments
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	639,631	536,583
Fixed maturity securities-available for sale	331,242	237,877
Equity securities	28	9,302
Cash and cash equivalents	90,956	123,077
Short-term investments	33,684	84,422
Other investments	11,748	10,591
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held to maturity	664,371	561,179
Fixed maturity securities-available for sale	331,242	237,877
Equity securities	28	9,302
Cash and cash equivalents	90,956	123,077
Short-term investments	33,684	84,422
Other investments	$ 11,748	$ 10,591

Amount of debt securities categorized neither as held-to-maturity nor trading.

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Amount of equity securities categorized neither as held-to-maturity nor as trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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-Glossary Cash

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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