Investment Securities - Allowance for Credit Losses for HTM Securities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning Balance (less than $1 million for 12/31/2020)	$ 1	$ 7	$ 1
(Reduction of) Provision for credit losses	4	(1)	5
Ending Balance	$ 5	6	$ 5
Accrued interest receivable		222		$ 171
Accrued interest receivable and other assets | Held-to-maturity Securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Accrued interest receivable		220		$ 225
Municipal bonds and notes
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning Balance (less than $1 million for 12/31/2020)		1
Ending Balance		1
Corporate bonds
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Beginning Balance (less than $1 million for 12/31/2020)		6
Ending Balance		$ 5