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Reinsurance - Narrative (Details) - USD ($) $ in Thousands |  | 1 Months Ended | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Apr. 01, 2019 | Jul. 31, 2018 | May 31, 2017 | Jun. 30, 2019 | Mar. 31, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018 | Dec. 31, 2017
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Restricted cash |  |  |  | $ 1,430 |  |  | $ 1,430 |  | $ 1,414 |
Reinsurance recoverable on unpaid claims |  |  |  | $ 3,775 |  | $ 2,382 | $ 3,775 | $ 2,382 | $ 3,001 | $ 1,902
ILN Transactions |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Optional termination right, percent of reinsurance coverage threshold |  |  |  | 10.00% |  |  | 10.00% |  |  |
Mortgage-linked Debt | 2017 ILN Notes | Oaktown Re Ltd |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of notes |  |  | $ 211,300 |  |  |  |  |  |  |
Mortgage-linked Debt | 2018 ILN Notes | Oaktown Re Ltd |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of notes |  | $ 264,500 |  |  |  |  |  |  |  |
Third-Party Reinsurers | 2017 ILN Transaction |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate excess of loss reinsurance coverage |  |  |  |  |  |  | $ 91,500 |  |  |
Aggregate excess of loss reinsurance retained by company |  |  | 126,800 |  |  |  | 124,400 |  |  |
Risk premiums paid |  |  |  | $ 1,300 |  | $ 1,600 | 2,600 | $ 3,300 |  |
Third-Party Reinsurers | 2017 ILN Transaction | Maximum |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate excess of loss reinsurance coverage |  |  | $ 211,300 |  |  |  |  |  |  |
Reinsurance coverage, term of underlying mortgage amortization (in years) |  |  | 10 years |  |  |  |  |  |  |
Anticipated payment related to annual operating expenses |  |  |  |  |  |  | 300 |  |  |
Third-Party Reinsurers | 2018 ILN Transaction |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate excess of loss reinsurance coverage |  |  |  |  |  |  | 258,200 |  |  |
Aggregate excess of loss reinsurance retained by company |  | 125,300 |  |  |  |  | 125,200 |  |  |
Risk premiums paid |  |  |  | 1,600 |  |  | $ 3,300 |  |  |
Third-Party Reinsurers | 2018 ILN Transaction | Maximum |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Aggregate excess of loss reinsurance coverage |  | $ 264,500 |  |  |  |  |  |  |  |
Reinsurance coverage, term of underlying mortgage amortization (in years) |  | 10 years |  |  |  |  |  |  |  |
Anticipated payment related to annual operating expenses |  |  |  |  | $ 250 |  |  |  |  |
Third-Party Reinsurers | QSR Transactions |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Ceding commissions under 2016 QSR Transaction |  |  |  |  |  |  | 20.00% |  |  |
Third-Party Reinsurers | 2018 QSR Transaction |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Threshold for loss ratio on loans to qualify for profit commission |  |  |  |  |  |  | 61.00% |  |  |
Reinsurance recoverable on unpaid claims |  |  |  | $ 1,100 |  |  | $ 1,100 |  |  |
Third-Party Reinsurers | Risk Written Policies in 2018 |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums earned under 2018 QSR Transaction |  |  |  |  |  |  | 25.00% |  |  |
Third-Party Reinsurers | Risk Written Policies in 2019 |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums ceded under QSR Transaction |  |  |  |  |  |  | 20.00% |  |  |
Third-Party Reinsurers | 2016 QSR Transaction |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums ceded under QSR Transaction |  |  |  | 20.50% | 25.00% |  |  |  |  |
Previously ceded primary RIF recaptured | $ 500,000 |  |  |  |  |  |  |  |  |
Threshold for loss ratio on loans to qualify for profit commission |  |  |  |  |  |  | 60.00% |  |  |
Reinsurance recoverable on unpaid claims |  |  |  | $ 2,700 |  |  | $ 2,700 |  |  |
Third-Party Reinsurers | Existing Risk Written Policies |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums ceded under QSR Transaction |  |  |  |  |  |  | 25.00% |  |  |
Third-Party Reinsurers | Fannie Mae |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums ceded under QSR Transaction |  |  |  |  |  |  | 100.00% |  |  |
Third-Party Reinsurers | Risk Written Policies from September 1, 2016 through December 31, 2017 |  |  |  |  |  |  |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of premiums ceded under QSR Transaction |  |  |  |  |  |  | 25.00% |  |  |

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