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INVESTMENTS - Net Effect on Shareholders' Equity of Unrealized Gains and Losses from Investment Securities (Detail) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
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Sep. 30, 2021 | Dec. 31, 2020
Investments [Abstract] |  |
Unrealized gains (losses) on securities available for sale | $ 13,494 | $ 14,290
Deferred income taxes | (3,763) | (3,929)
Shareholders' equity, unrealized gains (losses) on fixed maturity securities | $ 9,731 | $ 10,361

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- Definition Amount, after tax, of accumulated unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e681-108580 + Details
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