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Reserve for Loss and Loss Expense (Roll Forward of Gross and Net Asbestos and Net Environmental Incurred Losses and Loss Expenses and Related Reserves) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Reserve for loss and loss expense at beginning of year, gross | $ 28,415 | $ 29,962 | $ 30,411
Incurred loss and loss expense, gross | 3,059 | 126 | 1,483
Less: loss and loss expense paid, gross | (1,454) | (1,673) | (1,932)
Reserve for loss and loss expense at the end of year, gross | 30,020 | 28,415 | 29,962
Reserve for loss and loss expense at beginning of year, net | 21,212 | 22,716 | 23,161
Incurred loss and loss expense, net | 2,877 | 0 | 1,380
Less: loss and loss expense paid, net | (1,306) | (1,504) | (1,825)
Reserve for loss and loss expense at the end of year, net | 22,783 | 21,212 | 22,716
Asbestos [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Reserve for loss and loss expense at beginning of year, gross | 7,577 | 7,847 | 8,024
Incurred loss and loss expense, gross | 0 | 0 | (77)
Less: loss and loss expense paid, gross | (249) | (270) | (254)
Reserve for loss and loss expense at the end of year, gross | 7,328 | 7,577 | 7,847
Reserve for loss and loss expense at beginning of year, net | 6,346 | 6,615 | 6,793
Incurred loss and loss expense, net | 0 | 0 | 77
Less: loss and loss expense paid, net | (249) | (269) | (255)
Reserve for loss and loss expense at the end of year, net | 6,097 | 6,346 | 6,615
Enviromental [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Reserve for loss and loss expense at beginning of year, gross | 20,838 | 22,115 | 22,387
Incurred loss and loss expense, gross | 3,059 | 126 | 1,406
Less: loss and loss expense paid, gross | (1,205) | (1,403) | (1,678)
Reserve for loss and loss expense at the end of year, gross | 22,692 | 20,838 | 22,115
Reserve for loss and loss expense at beginning of year, net | 14,866 | 16,101 | 16,368
Incurred loss and loss expense, net | 2,877 | 0 | 1,303
Less: loss and loss expense paid, net | (1,057) | (1,235) | (1,570)
Reserve for loss and loss expense at the end of year, net | $ 16,686 | $ 14,866 | $ 16,101

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- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, before estimated recoveries from reinsurers. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 + Details
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- Definition Amount, before effects of reinsurance, of expense for claims incurred and costs incurred in the claim settlement process attributable to asbestos and environmental claims. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 + Details
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- Definition Amount of cash outflow to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585 + Details
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- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 + Details
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- Definition Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 + Details
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