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Investments - Gross Unrealized Gains and Losses and Cost and Fair Value of Investments Classified as Available-for-sale (Detail) (USD $) In Thousands, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
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Investment [Line Items] |  |
Cost or Amortized Cost | $ 215,468 | $ 151,514
Gross Unrealized Gains | 2,953 | 6,101
Gross Unrealized Losses | (5,549) | (1,710)
Securities available for sale/Available-for-sale, Fair Value | 212,872 | 155,905
States and political subdivisions [Member] |  |
Investment [Line Items] |  |
Cost or Amortized Cost | 132,603 | 93,362
Gross Unrealized Gains | 2,229 | 5,022
Gross Unrealized Losses | (2,567) | (142)
Securities available for sale/Available-for-sale, Fair Value | 132,265 | 98,242
Corporate bonds [Member] |  |
Investment [Line Items] |  |
Cost or Amortized Cost | 58,566 | 39,211
Gross Unrealized Gains | 377 | 623
Gross Unrealized Losses | (273) | (24)
Securities available for sale/Available-for-sale, Fair Value | 58,670 | 39,810
U.S. agency-based mortgage-backed securities [Member] |  |
Investment [Line Items] |  |
Cost or Amortized Cost | 10,418 | 11,941
Gross Unrealized Gains | 2 | 5
Gross Unrealized Losses | (1,981) | (859)
Securities available for sale/Available-for-sale, Fair Value | 8,439 | 11,087
Total fixed maturity [Member] |  |
Investment [Line Items] |  |
Cost or Amortized Cost | 201,587 | 144,514
Gross Unrealized Gains | 2,608 | 5,650
Gross Unrealized Losses | (4,821) | (1,025)
Securities available for sale/Available-for-sale, Fair Value | 199,374 | 149,139
Equity Securities [Member] |  |
Investment [Line Items] |  |
Cost or Amortized Cost | 13,881 | 7,000
Gross Unrealized Gains | 345 | 451
Gross Unrealized Losses | (728) | (685)
Securities available for sale/Available-for-sale, Fair Value | $ 13,498 | $ 6,766

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- Definition Amount of accumulated pre-tax unrealized gain before deducting pre-tax unrealized losses on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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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) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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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 + Details
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