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Loss and Loss Adjustment Expenses - Summary Exposures to Various Asbestos Related Claims (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Asbestos Claims [Line Items] |  |  |
Reserves for loss and LAE at beginning of year | $ 570,450 | $ 538,214 | $ 532,204
Incurred losses and LAE during the current year | 228,973 | 219,903 | 189,706
Less loss and LAE payments for claims occurring during the current year | 44,474 | 50,423 | 53,213
Reserves for loss and LAE | 614,557 | 570,450 | 538,214
Asbestos Issue [Member] |  |  |
Asbestos Claims [Line Items] |  |  |
Reserves for loss and LAE at beginning of year | 167 |  |
Incurred losses and LAE during the current year | 53 | 168 |
Less loss and LAE payments for claims occurring during the current year | 1 | 1 |
Reserves for loss and LAE | $ 219 | $ 167 |

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- Definition Amount of payments made in the reporting period to settle claims incurred in the current period and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 403 -Paragraph 04 -Subparagraph b Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 + Details
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- Definition The estimated cost of settling claims under the terms of the underlying insurance policies and assumed and ceded insurance contracts as of the balance sheet date, including an estimate for claims which have been incurred but not reported and the actual and estimated costs of settling claims. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 403 -Paragraph 04 -Subparagraph b + Details
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- Definition Total provision in the period for claims incurred and costs incurred in the claim settlement process. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 403 -Paragraph 04 -Subparagraph b Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 + Details
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