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Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Detail) - Successor [Member] - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities | $ 5,855,962 | $ 6,049,908
Ambac insured Re-remic [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Coupon rate | 1.48% |
Fair Value Inputs Maturity | 4 years 3 months 26 days |
Yield | 0.00% |
Variable Interest Entity, Primary Beneficiary [Member] | United States Transactions [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Coupon rate | 5.88% | 5.88%
Fair Value Inputs Maturity | 20 years 7 months 5 days | 20 years 8 months 68 days
Yield | 5.95% | 5.86%
Fair Value, Inputs, Level 3 [Member] | RMBS Cash Flows Consisting of Deferred Amounts [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities | $ 628,986 | $ 696,713
Fair Value, Inputs, Level 3 [Member] | RMBS priced using discounted cash flows [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities | 26,831 |
Fair Value, Inputs, Level 3 [Member] | Ambac insured Re-remic [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities |  | 0
Fair Value, Inputs, Level 3 [Member] | Corporate Obligations [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities | 0 | 0
Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Corporate Obligations [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Available-for-sale Securities | $ 2,663,719 | $ 2,622,566

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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562 + Details
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