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Loss Reserves - Narrative (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 USD ($) loan | Dec. 31, 2016 USD ($) loan | Dec. 31, 2015 USD ($) loan
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Premium refund liability, expected claim payments | $ 61,000 | $ 85,000 |
Other items removed from inventory | loan | 1,337 | 1,273 | 1,121
Losses for unpaid claims and adjustment expense | $ 493,300 | $ 689,258 | $ 823,058
Percent of inventory in default for more than 36 consecutive months | 45.00% | 47.00% | 50.00%
Pool insurance notice inventory (in number of loans) | loan | 1,309 | 1,883 | 2,739
Settlements for commutations of coverage, pools of nonperforming loans |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Losses for unpaid claims and adjustment expense | $ 54,000 |  |
Settlements for commutations of coverage, pools of nonperforming loans, and claims paying practices |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Losses for unpaid claims and adjustment expense |  | $ 53,000 |
Payments for settlements |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Losses for unpaid claims and adjustment expense |  |  | $ 10,000
Payments for settlements | Freddie Mac |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Losses for unpaid claims and adjustment expense |  | $ 42,000 | $ 42,000
Decrease in estimated claim rate on primary delinquencies |  |  |
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |  |
Percentage of prior year default inventory resolved (in hundredths) | 67.00% | 63.00% | 60.00%

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- Definition The percentage of the prior year default inventory resolved, which is used in the calculation of the change in the severity and claim rates. + References No definition available. + Details
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- Definition The number of loans included in the pool insurance notice inventory as of the end of the reporting period. + References No definition available. + Details
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- Definition The carrying amount for the estimate of premiums to be refunded on expected claim payments. + References No definition available. + Details
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- Definition Other deductions from the primary default inventory, including items removed for settlements + References No definition available. + Details
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- Definition Primary Default Inventory Twelve Months Or More, Percent Of Primary Default Inventory In Default For Twelve Months Or More In Default For More Than Thirty Six Consecutive Months + References No definition available. + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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