Investments (HTM Year of Issuance and Risk Grade) (Details) $ in Millions	Sep. 30, 2021 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
2021	$ 96
2020	124
2019	10
2018	0
2017	8
Prior	221
Total Securities	459
Pass
Schedule of Held-to-maturity Securities [Line Items]
2021	96
2020	124
2019	10
2018	0
2017	8
Prior	220
Total Securities	458
Accruing substandard
Schedule of Held-to-maturity Securities [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	1
Total Securities	$ 1

Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
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