Investments - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2022 USD ($) investment	Dec. 31, 2021 USD ($) investment
Investment [Line Items]
Percentage of securities representing gross unrealized losses (as a percent)	13.00%	2.00%
Percentage of gross unrealized losses in a continuous loss position less than twelve months (as a percent)	76.00%	94.00%
Individual securities comprising total gross unrealized losses \| investment	3,874	1,202
Percentage of residential mortgage-backed holdings exposure to sub-prime mortgage collateral (as a percent)	36.00%
Minimum
Investment [Line Items]
Total	$ 0.1	$ 0.1
Maximum
Investment [Line Items]
Total	$ 9.5	$ 9.6

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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-Section 50
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-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
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-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922355-210448

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
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+ Details