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v3.23.3

Commitments and Contingencies - Schedule of Fair Value, Off-balance Sheet Risks (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Financing assets (excluding leases) |  |
Other Commitments [Line Items] |  |
Credit related commitments | $ 62,689 | $ 23,452
Standby letters of credit |  |
Other Commitments [Line Items] |  |
Credit related commitments | 2,721 | 436
Other letters of credit |  |
Other Commitments [Line Items] |  |
Credit related commitments | 114 | 44
Deferred Purchase Agreements |  |
Other Commitments [Line Items] |  |
Credit related commitments | 2,087 | 2,039
Lessor commitments |  |
Other Commitments [Line Items] |  |
Credit related commitments | $ 1,014 | $ 941

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- Definition Credit Extension Commitments, Notional Amount + References No definition available. + Details
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Namespace Prefix: | fcnca_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |