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Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail) - USD ($) $ in Millions | Jun. 30, 2020 | Dec. 31, 2019
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Standard & Poor's, B Rating [Member] | Ambac Assurance Corporation [Member] |  |
Schedule of Investments [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | $ 1,220 |
Standard & Poor's, B- Rating [Member] |  |
Schedule of Investments [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors | $ 1,228 | $ 1,164
Standard & Poor's, B- Rating [Member] | Ambac Assurance Corporation [Member] |  |
Schedule of Investments [Line Items] |  |
Fair value of securities that include benefit of guarantees provided by financial guarantors |  | $ 1,153

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- Definition Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 210 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-12C.Column C.7) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611225-123010 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14.Column E.2,3) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611322-123010 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-12.Column C.3,4) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611133-123010 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 5 -Subparagraph (SX 210.12-13.Column C.6) -URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611282-123010 + Details
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