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Loans - Asset Quality Indicators (Details) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
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PD Grade 1 |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Lowest expected default probability | 1 |
Special Mention |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 13 |
Substandard |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 14 |
Doubtful |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 15 |
Loss |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 16 |
Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loans | $ 24,388,108,000 | $ 20,545,198,000
Commercial | Special Mention |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 13 |
Minimum | Pass |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 1 |
Minimum | Special Mention |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 13 |
Minimum | Loan Reassessed |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loans | $ 1,000,000 |
Minimum | PD Grade 13 |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loans | $ 500,000 |
Minimum | LGD Grade 1 |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 1 |
Minimum | Commercial | Pass |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 1 |
Maximum | Pass |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 12 |
Maximum | Loss |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 16 |
Maximum | LGD Grade 12 |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 12 |
Maximum | Commercial | Pass |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Commercial loan grades | 16 |

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- Definition The PD grade that has the lowest expected default probability. + References No definition available. + Details
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- Definition Amount, before allowance and fees, of loans and leases receivable. 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=118952595&loc=d3e4428-111522 + Details
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