Investments - Gross Unrealized Gains and Losses and Cost or Amortized Cost and Fair Value of Investments Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	$ 374,748	$ 337,004
Available-for-Sale, Gross Unrealized Gains	9,244	9,508
Available-for-Sale, Gross Unrealized Losses	(2,369)	(3,494)
Available-for-Sale, Fair Value	381,623	343,018
Total Fixed Maturity [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	364,748	327,004
Available-for-Sale, Gross Unrealized Gains	7,454	7,732
Available-for-Sale, Gross Unrealized Losses	(2,369)	(3,494)
Available-for-Sale, Fair Value	369,833	331,242
Other Investments [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	10,000	10,000
Available-for-Sale, Gross Unrealized Gains	1,759	1,748
Available-for-Sale, Fair Value	11,759	11,748
States and Political Subdivisions [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	166,520	151,744
Available-for-Sale, Gross Unrealized Gains	6,685	7,302
Available-for-Sale, Gross Unrealized Losses	(447)	(1,672)
Available-for-Sale, Fair Value	172,758	157,374
Corporate Bonds [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	189,169	165,412
Available-for-Sale, Gross Unrealized Gains	762	428
Available-for-Sale, Gross Unrealized Losses	(451)	(470)
Available-for-Sale, Fair Value	189,480	165,370
U.S. Agency-Based Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	9,059	9,848
Available-for-Sale, Gross Unrealized Gains	7	2
Available-for-Sale, Gross Unrealized Losses	(1,471)	(1,352)
Available-for-Sale, Fair Value	7,595	8,498
Equity Securities [Member]
Investment [Line Items]
Available-for-Sale, Gross Unrealized Gains	31	28
Available-for-Sale, Fair Value	$ 31	$ 28

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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