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Commitments and Contingencies - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2012 | Jun. 30, 2021 | Dec. 31, 2020
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Unfunded commitments credit loss (reversal) provision |  | $ 0 |  | $ (1,200,000) |  |  |  |
(Reversal of) provision for credit losses on unfunded loan commitments |  | 0 | $ 248,000 | (1,202,000) | $ 610,000 |  |  |
Litigation Matters |  |  |  |  |  |  |  |
Restricted cash and cash equivalents | [1] | $ 0 | $ 0 | $ 0 | $ 0 |  |  |
Visa Inc. |  |  |  |  |  |  |  |
Litigation Matters |  |  |  |  |  |  |  |
Settlement agreement amount |  |  |  |  |  | $ 4,000,000,000 |  |
Restricted cash and cash equivalents |  |  |  |  |  |  | $ 894,000,000 |
Minimum |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Weighted average remaining term (in years) |  | 1 year |  | 1 year |  |  |  |
Finance lease, initial contract terms (in years) |  | 3 years |  | 3 years |  |  |  |
Maximum |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Weighted average remaining term (in years) |  | 11 years |  | 11 years |  |  |  |
Finance lease, initial contract terms (in years) |  | 4 years |  | 4 years |  |  |  |
Total commitments and standby letters of credit | Interest payable and other liabilities |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |
Allowance for off balance sheet commitments |  | $ 1,600,000 |  | $ 1,600,000 |  |  |  | $ 2,800,000
[1] | Restricted cash includes reserve requirements held with the Federal Reserve Bank of San Francisco. In response to the COVID-19 pandemic, the Federal Reserve reduced the reserve requirement ratios to zero percent effective March 26, 2020.

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