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Reinsurance - Narrative (Details) - USD ($) |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Ceded premiums |  | $ 28,440,000 |  | $ 25,327,000 | $ 100,260,000 | $ 79,970,000
Quota Share Reinsurance Agreement, 2019 |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Contingent termination fee |  |  |  |  | $ 0 |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) |  |  |  |  | 90.00% |
Quota share for all policies covered (as a percent) |  |  |  |  | 30.00% |
Cede rate, option 1 (as a percent) |  |  |  |  | 25.00% |
Cede rate, option 2 (as a percent) |  |  |  |  | 20.00% |
Ceding commission, percentage (as a percent) |  |  |  |  | 20.00% |
Loss ratio threshold for profit commissions (as a percent) |  |  |  |  | 62.00% |
Quota Share Reinsurance Agreement, 2015 |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Contingent termination fee |  | $ 0 | $ 6,800,000 |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) |  | 90.00% |  |  |  |
Quota share for all policies covered (as a percent) | 30.00% | 15.00% |  |  |  |
Loss ratio threshold for profit commissions (as a percent) |  | 68.00% |  |  |  |
Excess of Loss Reinsurance Agreement, Home Re |  |  |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |  |  |
Ceded premiums |  | $ 5,400,000 |  |  | $ 12,400,000 |

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- Definition Amount of earned premiums ceded to other entities. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column C)) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84167274&loc=d3e27175-158546 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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