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Investment Securities - Additional Information (Details) - USD ($) $ in Millions			3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2020	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Decrease in AOCI	$ 3,679	$ 1,156	$ 3,679	$ (660)		$ (1,263)
Increase in retained earnings	(36,552)	(40,340)	(36,552)
Accrued interest receivable			244
Proceeds from Sale of Available-for-sale Securities			144	3,100
Debt Securities, Available-for-sale, Gain (Loss)			1	$ 24
Derivative, collateral, obligation to return securities	$ 1	$ 1	1
Investment securities portfolio | US Treasury and Agency securities
Debt Securities, Available-for-sale [Line Items]
Percentage of portfolio	97.00%	96.00%
Collateral pledged
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, restricted	$ 13,600	$ 14,000	$ 13,600
Adjustment amount
Debt Securities, Available-for-sale [Line Items]
Decrease in AOCI					$ (11)
Increase in retained earnings					$ (11)

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