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Significant Group Concentrations of Credit Risk Significant Group Concentrations of Credit Risk (Commercial Real Estate Exposure) (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans |  | $ 49,285 | $ 52,291
Real estate construction loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans |  | 2,948 | 4,082
Commercial mortgage |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans |  | 11,255 | 9,912
Total commercial real estate |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans |  | 14,203 | 13,994
Total unused commitments |  | 4,030 | 3,272
Commercial Real Estate business line | Real estate construction loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans | [1] | 2,391 | 3,657
Commercial Real Estate business line | Commercial mortgage |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans | [1] | 3,338 | 2,273
Other Business Lines Member | Real estate construction loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans | [2] | 557 | 425
Other Business Lines Member | Commercial mortgage |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Total loans | [2] | $ 7,917 | $ 7,639
[1] | Primarily loans to real estate developers.
[2] | Primarily loans secured by owner-occupied real estate.

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- Definition Reflects unused commitments that have been issued to businesses to acquire real property, develop land for sale or construction thereon, to construct a facility and to provide financing on existing land or a building, which, pursuant to terms of the underlying debt instrument, are secured at a minimum but possibly exclusively by that real property. + References No definition available. + Details
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- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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 + Details
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