Investments and Cash - Distribution of Fixed-Maturity Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Amortized cost	$ 9,058	$ 9,639
Estimated Fair Value
Estimated Fair Value	9,451	10,122
Fixed Maturities [Member]
Amortized Cost
Due within one year	338
Due after one year through five years	1,577
Due after five years through 10 years	1,994
Due after 10 years	3,295
Amortized cost	8,237	8,371
Estimated Fair Value
Due within one year	335
Due after one year through five years	1,631
Due after five years through 10 years	2,078
Due after 10 years	3,540
Estimated Fair Value	8,630	8,854
Fixed Maturities [Member] \| RMBS [Member]
Amortized Cost
Amortized cost	649	745
Estimated Fair Value
Estimated Fair Value	635	775
Fixed Maturities [Member] \| CMBS [Member]
Amortized Cost
Amortized cost	384	402
Estimated Fair Value
Estimated Fair Value	$ 411	$ 419

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Amount 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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 210
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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