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Reserve for Losses and Loss Adjustment Expenses - Prior year development (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 59,250 | $ 44,067 | $ 100,922 | $ 63,090
Operating segments | Insurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 4,000 | $ 2,500 | $ 8,100 | $ 3,600
Percentage of prior year development | 0.50% | 0.40% | 0.50% | 0.30%
Operating segments | Insurance | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | $ 11,500 | $ 49,400 | $ 15,400
Operating segments | Insurance | Short tailed lines | Property excluding marine |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 7,100 | 7,500 | 21,600 | 9,600
Operating segments | Insurance | Short tailed lines | Travel and accident |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 6,700 | 3,500 | 9,300 |
Operating segments | Insurance | Short tailed lines | Lenders products |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 10,700 |  | 18,600 | 3,100
Operating segments | Insurance | Medium tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (24,500) | (17,100) | (45,400) | (25,100)
Operating segments | Insurance | Medium tailed lines | Programs |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (4,000) | (12,600) | (6,300)
Operating segments | Insurance | Medium tailed lines | Professional liability |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (6,300) | (11,200) |
Operating segments | Insurance | Medium tailed lines | Contract binding |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (20,100) | (6,100) | (20,100) | (19,300)
Operating segments | Insurance | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 8,100 |  | 13,300
Operating segments | Insurance | Long tailed lines | Construction and national accounts |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 5,600 |  |  |
Operating segments | Insurance | Long tailed lines | Executive assurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 2,400 |  |
Operating segments | Insurance | Long tailed lines | Other product lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 4,900 |  | 7,600
Operating segments | Insurance | Short tailed and long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 28,500 | 19,700 | 53,500 | 28,700
Operating segments | Reinsurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 20,500 | $ 40,200 | $ 47,300 | $ 51,800
Percentage of prior year development | 2.80% | 8.40% | 3.40% | 5.10%
Operating segments | Reinsurance | Short tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | $ 46,200 | $ 67,200 | $ 65,700
Operating segments | Reinsurance | Short tailed lines | Property catastrophe and property other than property catastrophe |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | 18,300 | 28,800 |
Operating segments | Reinsurance | Short tailed lines | Property catastrophe |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ (17,100) |  | (39,600) | 21,300
Operating segments | Reinsurance | Short tailed lines | Other specialty lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 61,600 | 27,500 | 78,200 | 39,300
Operating segments | Reinsurance | Medium tailed lines | Marine and aviation |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 4,000 |  |  |
Operating segments | Reinsurance | Long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (33,200) |  | (24,800) | (15,600)
Operating segments | Reinsurance | Long tailed lines | Casualty |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | (34,200) | (5,800) |  |
Operating segments | Reinsurance | Short tailed and medium tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 53,700 |  | 72,100 | 67,400
Operating segments | Reinsurance | Medium tailed and long tailed lines |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  | (6,000) |  |
Operating segments | Mortgage |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 43,100 | $ 200 | $ 54,000 | $ 6,300
Percentage of prior year development | 12.90% | 0.10% | 8.10% | 0.90%
Operating segments | Other |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ (8,300) | $ 1,100 | $ (8,400) | $ 1,300

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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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