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Loans and Leases - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2020 | Sep. 30, 2020 | Dec. 31, 2019 | Jun. 30, 2020 | Sep. 30, 2019 | Jun. 30, 2019 | Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Accrued interest | $ 177,500 | $ 177,500 | $ 84,600 |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 59,706,531 | 59,706,531 | 31,061,111 |  |  |  |
Troubled debt restructurings loans | 321,400 | 321,400 | 206,300 |  |  |  |
Allowance for loan and lease losses | 988,102 | 988,102 | 200,307 | $ 537,881 | $ 193,149 | $ 192,749 | $ 180,424
Bank Overdrafts | 9,000 | 9,000 | 8,100 |  |  |  |
Net loans and leases | 58,718,429 | 58,718,429 | 30,860,804 |  |  |  |
Asset Pledged as Collateral |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Net loans and leases | 39,400,000 | 39,400,000 | 19,200,000 |  |  |  |
SunTrust Banks, Inc. Branches |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Financing Receivables | 423,400 | 423,400 |  |  |  |  |
Allowance For TDRs To Recorded Investment Of TDRs |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses | $ 12,600 | $ 12,600 | $ 19,700 |  |  |  |
Ratio of the allowance for loan losses to loans | 4.00% | 4.00% | 10.00% |  |  |  |
Loans Held For Sale, Residential Real Estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Troubled debt restructurings loans | $ 44,100 | $ 44,100 | $ 51,100 |  |  |  |
Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 33,655,717 | 33,655,717 | 20,051,091 |  |  |  |
Allowance for loan and lease losses |  |  | 158,598 |  |  |  |
Allowance - purchased credit-impaired loans |  |  | 848 |  |  |  |
Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 28,048,649 | 28,048,649 | 15,640,208 |  |  |  |
Allowance for loan and lease losses | 489,094 | 489,094 | 122,486 | 318,722 | 114,130 | 116,096 | 98,947
Consumer |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 12,327,869 | 12,327,869 | 6,177,139 |  |  |  |
Consumer | Consumer Real Estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 12,327,869 | 12,327,869 | 6,177,139 |  |  |  |
Allowance for loan and lease losses | 265,430 | 265,430 | 28,443 | 143,757 | 30,674 | 31,532 | 37,439
Consumer | Credit Card and Other |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 1,212,058 | 1,212,058 | 495,864 |  |  |  |
Allowance for loan and lease losses | $ 25,620 | $ 25,620 | 13,266 | 18,117 | $ 12,720 | $ 12,168 | $ 12,727
Residential Portfolio Segment [Member] | Real Estate Loan [Member] |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Percentage contributed in total loan | 21.00% | 21.00% |  |  |  |  |
TRUPS | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 209,400 | $ 209,400 | 218,300 |  |  |  |
Allowance for loan and lease losses | 18,200 | 18,200 | 19,100 |  |  |  |
Credit Card | Consumer | Credit Card and Other |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 270,511 | 270,511 | 201,171 |  |  |  |
Finance And Insurance Companies | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 3,100,000 | $ 3,100,000 |  |  |  |  |
Percentage of commercial & industrial loan portfolio | 9.00% | 9.00% |  |  |  |  |
Percentage contributed in total loan | 5.00% | 5.00% |  |  |  |  |
Loans to mortgage companies | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 5,607,068 | $ 5,607,068 | 4,410,883 |  |  |  |
Percentage of commercial & industrial loan portfolio | 17.00% | 17.00% |  |  |  |  |
Percentage contributed in total loan | 9.00% | 9.00% |  |  |  |  |
Percentage Contributed | 26.00% | 26.00% |  |  |  |  |
C&I |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Collateral for secured borrowings | $ 247,700 | $ 247,700 |  |  |  |  |
Allowance for credit loss, writeoff, collateral | 18,100 | 31,100 |  |  |  |  |
C&I | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 28,048,649 | 28,048,649 | 15,614,283 |  |  |  |
HELOC |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Collateral for secured borrowings | 9,700 | 9,700 |  |  |  |  |
HELOC | Consumer | Consumer Real Estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | 2,549,837 | 2,549,837 | 1,286,875 |  |  |  |
R/E Installment Loans |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Collateral for secured borrowings | 26,200 | 26,200 |  |  |  |  |
R/E Installment Loans | Consumer | Consumer Real Estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 9,778,032 | $ 9,778,032 | 4,865,498 |  |  |  |
Financial Asset Acquired with Credit Deterioration |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  | 286,811 | 286,811 |  |  |
Allowance - purchased credit-impaired loans |  |  | 2,000 |  |  |  |
Allowance for loan and lease losses write-offs, net |  |  | 5,800 |  |  |  |
Provision for loan, lease, and other losses |  |  | 1,300 |  |  |  |
Financial Asset Acquired with Credit Deterioration | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  | 137,702 | 137,702 |  |  |
Financial Asset Acquired with Credit Deterioration | Consumer | Consumer Real Estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  | 44,141 | 44,141 |  |  |
Financial Asset Acquired with Credit Deterioration | Consumer | Credit Card and Other |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  | 4,845 | $ 4,845 |  |  |
PD Grade 1 | Minimum | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Lowest expected default probability | 1 | 1 |  |  |  |  |
Loss | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 16 | 16 |  |  |  |  |
Loss | Maximum | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 16 | 16 |  |  |  |  |
Pass | Minimum | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 1 | 1 |  |  |  |  |
Pass | Maximum | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 12 | 12 |  |  |  |  |
Special Mention | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 13 | 13 |  |  |  |  |
Special Mention | Minimum | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 13 | 13 |  |  |  |  |
Substandard | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 14 | 14 |  |  |  |  |
Doubtful | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loan grades | 15 | 15 |  |  |  |  |
PD Grade 13 | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Allowance for loan and lease losses |  |  | $ 8,142 |  |  |  |
PD Grade 13 | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 534,483 | $ 534,483 |  |  |  |  |
Paycheck Protection Plan | Commercial | Commercial and industrial (a) |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans and leases (including $12,372 and $— at fair value, respectively) | $ 4,200,000 | $ 4,200,000 |  |  |  |  |

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