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Investment Securities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Accrued interest receivables on investment securities	$ 86			$ 86		$ 87
Impairment losses	0	$ 7	$ 0	7	$ 0
Securities with a fair value, pledged as collateral	11,000			11,000		11,000
Investment Holdings [Line Items]
Unrealized losses	83			83		37
Non-rated Securities
Investment Holdings [Line Items]
Unrealized losses	$ 1			$ 1		$ 1