For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of interest income on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), from change in present value of expected cash flows, attributable to passage of time.

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of obligation to return securities collateral under master netting arrangements that have not been offset against derivative assets.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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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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Investment Securities - Additional Information (Details) - USD ($) $ in Millions			3 Months Ended		12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Increase in retained earnings	$ 43,167	$ 40,088	$ 43,167		$ 40,088
Accrued interest receivable			237		230
Proceeds from sales			595	$ 144
Gross realized gains			4	$ 1
Derivative, collateral, obligation to return securities	$ 1	$ 1	1		1
Investment securities portfolio \| US Treasury and Agency securities
Debt Securities, Available-for-sale [Line Items]
Percentage of portfolio	96.00%	96.00%
Collateral pledged
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, restricted	$ 16,800	$ 16,500	$ 16,800		$ 16,500