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Investments - Summary of Net Investment Income (Detail) - Successor [Member] - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Sep. 30, 2015
Investment [Line Items] |  |  |  |
Fixed income securities | $ 81,831 | $ 67,293 | $ 207,358 | $ 197,506
Short-term investments | 194 | 85 | 1,124 | 186
Loans | 97 | 113 | 273 | 338
Investment expense | (2,592) | (1,872) | (6,875) | (6,801)
Securities available-for-sale and short-term | 79,530 | 65,619 | 201,880 | 191,229
Other investments | 11,387 | (1,424) | 20,616 | 10,702
Total net investment income | 90,917 | 64,195 | 222,496 | 201,931
Gains (losses) on securities held as of reporting date [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Net Realized and Unrealized Gain (Loss) on Trading Securities | 10,197 | (2,549) | 17,145 | 7,493
Trading Securities, Realized Gain (Loss) | 1,859 | 933 | 5,268 | 7,534
Other investments | $ 8,338 | $ (3,482) | $ 11,877 | $ (41)

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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 -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 3: 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=27723805&loc=d3e24721-111560 + Details
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