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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, unless otherwise specified | 3 Months Ended | 12 Months Ended
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Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Proceeds from sales |  |  |  |  |  |  |  |  | $ 10,990 | $ 33,140 | $ 36,329
Gross realized investment gains |  |  |  |  |  |  |  |  | 1,354 | 2,741 | 2,436
Gross realized investment (losses) |  |  |  |  |  |  |  |  | (471) |  | (99)
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | 883 | 2,741 | 2,337
Impairments |  |  |  |  |  |  |  |  | (2,229) |  | (169)
Other, including gains on calls and redemptions |  |  |  |  |  |  |  |  | 135 | 238 | 60
Net realized investment gains (losses) | 710 | (654) | (1,291) | 24 | 66 | 985 | 137 | 1,791 | (1,211) | 2,979 | 2,228
Fixed Maturity Securities Available for Sale [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Proceeds from sales |  |  |  |  |  |  |  |  | 2,090 | 22,363 | 21,560
Gross realized investment gains |  |  |  |  |  |  |  |  | 90 | 1,555 | 815
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | 90 | 1,555 | 815
Other, including gains on calls and redemptions |  |  |  |  |  |  |  |  | 38 | 15 |
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | 128 | 1,570 | 815
Equity securities [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Proceeds from sales |  |  |  |  |  |  |  |  | 8,900 | 10,777 | 14,769
Gross realized investment gains |  |  |  |  |  |  |  |  | 1,264 | 1,186 | 1,621
Gross realized investment (losses) |  |  |  |  |  |  |  |  | (471) |  | (98)
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | 793 | 1,186 | 1,523
Impairments |  |  |  |  |  |  |  |  | (2,229) |  |
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | (1,436) | 1,186 | 1,523
Other [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Proceeds from sales |  |  |  |  |  |  |  |  |  |  |
Gross realized investment gains |  |  |  |  |  |  |  |  |  |  |
Gross realized investment (losses) |  |  |  |  |  |  |  |  |  |  | (1)
Net realized investment gains (losses) |  |  |  |  |  |  |  |  |  |  | (1)
Impairments |  |  |  |  |  |  |  |  |  |  | (169)
Other, including gains on calls and redemptions |  |  |  |  |  |  |  |  | 97 | 223 | 60
Net realized investment gains (losses) |  |  |  |  |  |  |  |  | $ 97 | $ 223 | $ (110)

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- Definition Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill. + References 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=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2420-110228 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26805-111562 + Details
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- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 + Details
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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26853-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
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