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AVAILABLE-FOR-SALE DEBT SECURITIES - Summary of Available-for-Sale Debt Securities at Estimated Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2021 | Dec. 31, 2020
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Available-for-Sale Debt Securities |  |
Amortized Cost | $ 2,489 | $ 2,023
Gross Unrealized Gains | 1 | 3
Gross Unrealized Losses | (1) | 0
Estimated Fair Value | 2,489 | 2,026
U.S. treasury securities |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 360 | 308
Gross Unrealized Gains | 0 | 1
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 360 | 309
U.S. government agencies securities |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 5 | 0
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 5 | 0
Non-U.S. government securities |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 44 | 43
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 44 | 43
Certificates of deposit |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 361 | 216
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | 361 | 216
Corporate debt securities |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 1,272 | 1,140
Gross Unrealized Gains | 1 | 2
Gross Unrealized Losses | (1) | 0
Estimated Fair Value | 1,272 | 1,142
Residential mortgage and asset-backed securities |  |
Available-for-Sale Debt Securities |  |
Amortized Cost | 447 | 316
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Estimated Fair Value | $ 447 | $ 316

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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- Definition Amortized cost excluding accrued interest, after allowance for credit loss, of 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 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
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- Definition Amount excluding accrued interest, of 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 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
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