Loans and Allowance for Credit Losses: Loans and Unfunded Credit Commitments - Recorded Investment in Loans Modified in TDRs within Previous 12 months Subsequently Defaulted (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($)
Cash flow dependent and innovation C&I (Commercial and Industrial) \| Innovation C&I
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded investment in loans modified in TDRs	$ 4

Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953682-111524

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration