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Investment - Major Categories of the Company's Net Investment Income (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] |  |  |  |  |  |  |  |  |  |  |
Total gross investment income |  |  |  |  |  |  |  |  | $ 28,402 | $ 28,102 | $ 27,540
Investment expenses |  |  |  |  |  |  |  |  | (1,373) | (1,084) | (1,200)
Net investment income | 6,763 | 6,947 | 6,649 | 6,670 | 6,698 | 6,801 | 6,605 | 6,914 | 27,029 | 27,018 | 26,340
Other Investments [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total gross investment income |  |  |  |  |  |  |  |  | 803 |  |
Equity securities [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total gross investment income |  |  |  |  |  |  |  |  | 543 | 446 | 181
Fixed Maturity Securities Available for Sale [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total gross investment income |  |  |  |  |  |  |  |  | 26,422 | 27,167 | 26,769
Short-term Investments [Member] |  |  |  |  |  |  |  |  |  |  |
Investment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total gross investment income |  |  |  |  |  |  |  |  | $ 634 | $ 489 | $ 590

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- Definition Amount of expenses related to the generation of investment income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.2) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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- Definition Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.2) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 2 -Article 7 + Details
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