Investment Securities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Jan. 01, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amount of collateralized loan obligations transferred from AFS to HTM for capital management purposes	$ 164,200
HTM securities, allowance for credit losses	$ 78
Approximate percentage rated at least AA+	98.00%
Provision for credit losses	$ 68
Cumulative effect of change in accounting principles
Schedule of Held-to-maturity Securities [Line Items]
HTM securities, allowance for credit losses		$ 10
Unrealized gains/(losses) on investment securities
Schedule of Held-to-maturity Securities [Line Items]
Pretax unrealized gains included in AOCI on the securities at the date of transfer	$ 5,000

Debt Securities, Available-for-sale, Transfer to Held-to-maturity, Amount

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- Definition

Debt Securities, Held-To-Maturity, External Credit Rating, Percent Rated AA Plus Or Higher

+ References

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- Definition

Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

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Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount, before tax, of adjustment from accumulated other comprehensive income (loss) for amortization of gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from transfer to investment in debt security measured at amortized cost (held-to-maturity).

+ References

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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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