Securities (Narrative) (Details)	Sep. 30, 2021 USD ($) Security	Dec. 31, 2020 USD ($) Security
Investments Debt And Equity Securities [Abstract]
Amortized cost of securities excluding accrued interest	$ 25,000,000.0	$ 24,400,000
Securities classified as trading	0	0
Securities pledged as collateral	3,600,000,000	$ 3,400,000,000
Allowance for credit loss	$ 0
Securities that met the criteria of a credit loss event \| Security	0
Number of securities with market values below their cost basis \| Security	115	28

Available for sale securities amortized cost excluding accrued interest.

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Number of securities met criteria of credit loss event.

+ References

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Number of securities with market values below cost basis.

+ References

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- Definition

Amount of allowance for credit loss of accounts and financing receivables. Includes, but is not limited to, notes and loan receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5074-111524

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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