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Loss Reserves - Prior Year Loss Reserves (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | $ 19,604 | $ (71,006) | $ (167,366)
(Decrease) in estimated claim rate on primary delinquencies |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | (2,536) | (111,848) | (212,738)
Increase (decrease)in estimated severity on primary delinquencies |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | 13,535 | (434) | 28,528
Change in estimates related to pool reserves, LAE reserves, reinsurance and other |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior years | $ 8,605 | $ 41,276 | $ 16,844

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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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