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Investments - Summary of Net Investment Income (Detail) - Successor [Member] - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Investment [Line Items] |  |  |  |
Net Realized and Unrealized Gain (Loss) on Trading Securities | $ 3,632 | $ 3,000 |  |
Trading Securities, Realized Gain (Loss) | 344 | 2,070 |  |
Fixed income securities | 60,499 | 81,751 | $ 169,848 | $ 155,820
Short-term investments | 2,438 | 1,151 | 5,278 | 2,140
Loans | 179 | 85 | 367 | 174
Investment expense | (1,374) | (2,044) | (3,200) | (4,041)
Securities available-for-sale and short-term | 61,742 | 80,943 | 172,293 | 154,093
Other investments | 4,920 | 4,217 | 4,609 | 12,626
Total net investment income | 66,662 | 85,160 | 176,902 | 166,719
Gains (losses) on securities held as of reporting date [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Net Realized and Unrealized Gain (Loss) on Trading Securities |  |  | 2,053 | 10,211
Trading Securities, Realized Gain (Loss) |  |  | 1,325 | 3,698
Other investments | $ 3,288 | $ 930 | $ 728 | $ 6,513

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- Definition Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
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- Definition Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.2) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e24721-111560 + Details
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