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Allowance for Credit Losses - Schedule of Allowance for Credit Losses on Unfunded Commitments (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance | $ 178 | $ 225 | $ 225
Provision (benefit) for credit losses - unfunded commitments | 645 | (37) | 58
Allowance for credit losses, ending balance | 922 | 178 | 225
Adoption of ASC 326 |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance |  |  | (38)
Balance after adoption of ASC 326 |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance |  |  | 187
Financing assets (excluding leases) |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance | 12 | 13 | 1
Provision (benefit) for credit losses - unfunded commitments | 94 | (1) | 3
Allowance for credit losses, ending balance | 106 | 12 | 13
Financing assets (excluding leases) | CIT Group Inc. |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance | 59 |  |
Allowance for credit losses, ending balance |  | 59 |
Financing assets (excluding leases) | Adoption of ASC 326 |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance | 0 | 0 | 9
Allowance for credit losses, ending balance |  | 0 | 0
Financing assets (excluding leases) | Balance after adoption of ASC 326 |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |
Allowance for credit losses, beginning balance | $ 12 | 13 | 10
Allowance for credit losses, ending balance |  | $ 12 | $ 13

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- Definition Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
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