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Investments - A Summary of the Company's Realized Gains and Losses on Sales, Calls or Redemptions of Investments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Proceeds from sales									$ 4,432	$ 10,548	$ 10,990
Gross realized investment gains									177	750	1,354
Gross realized investment (losses)									(162)	(451)	(471)
Net realized investment gains									15	299	883
Impairments									(2,653)	(222)	(2,229)
Other, including gains on calls and redemptions									144	620	135
Net realized gains (losses) on investments	$ 24	$ 40	$ (2,617)	$ 59	$ 516	$ (152)	$ 232	$ 101	(2,494)	697	(1,211)
Fixed Maturity Securities Available for Sale [Member]
Investment [Line Items]
Proceeds from sales									4,432	768	2,090
Gross realized investment gains									177	1	90
Gross realized investment (losses)									(162)
Net realized investment gains									15	1	90
Impairments									(2,653)	(222)
Other, including gains on calls and redemptions									102	244	38
Net realized gains (losses) on investments									(2,536)	23	128
Equity Securities [Member]
Investment [Line Items]
Proceeds from sales										9,780	8,900
Gross realized investment gains										749	1,264
Gross realized investment (losses)										(451)	(471)
Net realized investment gains										298	793
Impairments											(2,229)
Net realized gains (losses) on investments										298	(1,436)
Other [Member]
Investment [Line Items]
Other, including gains on calls and redemptions									42	376	97
Net realized gains (losses) on investments									$ 42	$ 376	$ 97

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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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.

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The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

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