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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, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 44,067 | $ 38,185 | $ 63,090 | $ 77,617
Underwriting segments | Insurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 2,500 | $ 2,600 | $ 3,600 | $ 7,000
Percentage of prior year development | 0.40% | 0.40% | 0.30% | 0.60%
Underwriting 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 | $ 8,000 | $ 15,400 | $ 17,700
Underwriting segments | Insurance | Short tailed lines | Property insurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | 7,500 |  | 9,600 |
Underwriting 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) | 3,500 |  |  |
Underwriting 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) |  |  | 3,100 |
Underwriting 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) | (17,100) | (10,400) | (25,100) | (17,300)
Underwriting 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) | (15,500) | (6,300) | (23,200)
Underwriting 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) | (6,100) |  | (19,300) | (9,700)
Underwriting 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) |  |  |
Underwriting segments | Insurance | Medium 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) |  | 5,100 |  | 15,600
Underwriting 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) | 19,700 |  | 28,700 |
Underwriting 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 | 4,900 | 13,300 | 6,600
Underwriting 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 | 5,100 |  | 5,700
Underwriting 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 |
Underwriting segments | Reinsurance |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 40,200 | $ 12,700 | $ 51,800 | $ 11,000
Percentage of prior year development | 8.40% | 3.50% | 5.10% | 1.50%
Underwriting 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 | $ 1,800 | $ 65,700 | $ (4,300)
Underwriting 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 |  |  | (17,900)
Underwriting segments | Reinsurance | Short tailed lines | Property catastrophe and property other than property catastrophe | Typhoon Jebi |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | (16,000)
Underwriting 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) | 27,500 |  |  | 10,200
Underwriting 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) |  |  | 67,400 |
Underwriting segments | Reinsurance | Short tailed and medium tailed lines | Property catastrophe |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  | 21,300 |
Underwriting segments | Reinsurance | Short tailed and medium 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) |  |  | 39,300 |
Underwriting 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) | 10,900 |  | 15,300
Underwriting segments | Reinsurance | Medium tailed and long tailed lines | Casualty |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | 9,100
Underwriting segments | Reinsurance | Medium tailed and long tailed lines | Marine |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) |  |  |  | 6,200
Underwriting 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) |  |  | (15,600) |
Underwriting 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) | (5,800) |  |  |
Underwriting segments | Mortgage |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 200 | $ 22,800 | $ 6,300 | $ 59,400
Percentage of prior year development | 0.10% | 6.50% | 0.90% | 8.80%
Underwriting segments | Other |  |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Prior year development favorable (unfavorable) | $ 1,100 | $ 100 | $ 1,300 | $ 100

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