Fair Values - Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Investment securities:
Equity securities	$ 64	$ 66
Debt securities	2,168	2,120
Derivative, gross, assets	183	80
Total Assets	2,415	2,266
Liabilities
Derivatives, gross, liabilities	359	977
Total Liabilities	359	977
Level 1
Investment securities:
Equity securities	64	66
Debt securities	0	0
Derivative, gross, assets	0	0
Total Assets	64	66
Liabilities
Derivatives, gross, liabilities	0	0
Total Liabilities	0	0
Level 2
Investment securities:
Equity securities	0	0
Debt securities	2,094	2,046
Derivative, gross, assets	169	62
Total Assets	2,263	2,108
Liabilities
Derivatives, gross, liabilities	359	977
Total Liabilities	359	977
Level 3
Investment securities:
Equity securities	0	0
Debt securities	74	74
Derivative, gross, assets	14	18
Total Assets	88	92
Liabilities
Derivatives, gross, liabilities	0	0
Total Liabilities	$ 0	$ 0