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	Dec. 31, 2015	Dec. 31, 2014
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	$ 386,109	$ 337,004
Available-for-Sale, Gross Unrealized Gains	9,447	9,508
Available-for-Sale, Gross Unrealized Losses	(3,286)	(3,494)
Available-for-Sale, Fair Value	392,270	343,018
Total Fixed Maturity [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	376,109	327,004
Available-for-Sale, Gross Unrealized Gains	7,199	7,732
Available-for-Sale, Gross Unrealized Losses	(3,286)	(3,494)
Available-for-Sale, Fair Value	380,022	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	2,217	1,748
Available-for-Sale, Fair Value	12,217	11,748
States and Political Subdivisions [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	164,684	151,744
Available-for-Sale, Gross Unrealized Gains	6,942	7,302
Available-for-Sale, Gross Unrealized Losses	(207)	(1,672)
Available-for-Sale, Fair Value	171,419	157,374
Corporate Bonds [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	202,537	165,412
Available-for-Sale, Gross Unrealized Gains	253	428
Available-for-Sale, Gross Unrealized Losses	(1,486)	(470)
Available-for-Sale, Fair Value	201,304	165,370
U.S. Agency-Based Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-Sale, Cost or Amortized Cost	8,888	9,848
Available-for-Sale, Gross Unrealized Gains	4	2
Available-for-Sale, Gross Unrealized Losses	(1,593)	(1,352)
Available-for-Sale, Fair Value	7,299	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)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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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)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
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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)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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