Net Interest Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Interest income:
Interest-bearing deposits with banks	$ 9	$ (9)
Investment securities:
Investment securities available-for-sale	154	140
Investment securities held-to-maturity	171	180
Investment securities purchased under money market liquidity facility	0	4
Total investment securities	325	324
Securities purchased under resale agreements	10	10
Loans	172	141
Other interest-earning assets	5	5
Total interest income	521	471
Interest expense:
Interest-bearing deposits	(63)	(69)
Short-term borrowings under money market liquidity facility	0	4
Long-term debt	65	60
Other interest-bearing liabilities	10	9
Total interest expense	12	4
Net interest income	$ 509	$ 467