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Reinsurance - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Effects of Reinsurance [Line Items] |  |  |  |
Reinsurance recoverable on loss reserves | $ 102,901 | $ 25,756 | $ 95,042 | $ 21,641
Ceded premiums | $ 43,637 | 31,576 |  |
Quota Share Reinsurance Agreements |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Ceding commission, percentage (as a percent) | 20.00% |  |  |
Reinsurance, Quota Share Reinsurance Agreement, Terms, Annual Loss Ratio Cap | 300.00% |  |  |
Reinsurance, Quota Share Reinsurance Agreement, Terms, Lifetime Loss Ratio Cap | 200.00% |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) | 90.00% |  |  |
Reinsurance recoverable on loss reserves | $ 102,900 |  | $ 95,000 |
Credit Union QSR |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Threshold for private mortgage insurer eligibility requirements for termination election (less than) (as a percent) | 80.00% |  |  |
Excess of Loss Reinsurance Agreement, Home Re |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Ceded premiums | $ 10,300 | $ 4,700 |  |
Excess of Loss Reinsurance Agreement, Home Re | Minimum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Amortization period excess of loss reinsurance coverage | 10 years |  |  |
Excess of Loss Reinsurance Agreement, Home Re | Maximum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Amortization period excess of loss reinsurance coverage | 12 years 6 months |  |  |
Home Re special purpose insurers |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Percent of total trust assets invested in cash or direct U.S. federal government obligations | 99.50% |  |  |
Home Re special purpose insurers | Minimum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Term of mortgage insurance-linked notes | 10 years |  |  |
Home Re special purpose insurers | Maximum |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Term of mortgage insurance-linked notes | 12 years 6 months |  |  |
Financial Asset Equal To Or Greater Than 60 Days Past Due | Excess of Loss Reinsurance Agreement, Home Re |  |  |  |
Effects of Reinsurance [Line Items] |  |  |  |
Percent of delinquent reinsured loans to total reinsured loans | 4.00% |  |  |

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- Definition Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=99404803&loc=d3e21412-158489 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387 Reference 3: 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=116884095&loc=d3e14764-158437 Reference 4: 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=116884095&loc=d3e14764-158437 + Details
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