Investments - Investments - Purchased Financial Assets with Credit Deterioration (Details) $ in Millions	Sep. 30, 2020 USD ($)
Commercial Loan [Member]
Schedule of Investments [Line Items]
Certain Loans Acquired in Transfer Accounted for as Available-for-sale Debt Securities, Acquired, at Acquisition, at Fair Value	$ 0
Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Certain Loans Acquired in Transfer Accounted for as Available-for-sale Debt Securities, Acquired, at Acquisition, at Fair Value	$ 0

Fair value at acquisition of acquired loans accounted for as available-for-sale debt securities with evidence of deterioration of credit quality.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121585399&loc=d3e13503-111538

Name:	us-gaap_CertainLoansAcquiredInTransferAccountedForAsAvailableForSaleDebtSecuritiesAcquiredDuringPeriodAtAcquisitionAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant