Loans and Allowance for Credit Losses - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) loan loan_segment	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Number of loans and leases segments \| loan_segment	2
Loans and leases pledged as collateral	$ 8,070	$ 6,750
Number of loans on non-accrual status \| loan	0	0
Loan with principal or interest payments 30 days or more contractually past due \| loan	1	0
Sale of loans	$ 324	$ 131	$ 278
Loss on sale of loans	$ 41
Loans modified in troubled debt restructurings \| loan	0	0
Loans no longer meeting similar risk of collective pool \| loan	5	1
Loans no longer meeting similar risk of collective pool, amount	$ 77	$ 25
Allowance for credit loss	$ 122	74	67	$ 54
Investment grade loans	81.00%
Speculative grade loans	19.00%
Speculative senior secured loans with BB or B rating	85.00%
Provision (reversal) for credit loss	$ 88	10	$ 15
Leveraged Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Sale of loans	353
Commercial and Financial Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Allowance for credit loss	$ 6	$ 1

Financing Receivable Recorded Investment Equal To 30 Days or Greater

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Financing Receivable, Recorded Investment, Nonaccrual Status, Number of Loans

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Investment Grade Loans

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Loans And Leases Receivable, Number Of Loans And Leases Segments

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Loans No Longer Meeting Similar Risk of Collective Pool

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Number of Loans, No Longer Met Similar Risk

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Speculative Grade Loans

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Speculative Senior Secured Loans, with BB or B Rating

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- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Number of financing receivables that have been modified by troubled debt restructurings.

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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.

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Amount of gain (loss) on sale of financing receivable.

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Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

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The cash inflow associated with the sale of loans receivables arising from the financing of goods and services.

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Amount of credit loss expense (reversal of expense) for financing receivable.

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