Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Investment securities:
Equity securities	$ 81	$ 78
Debt securities	21,550	8,328
Derivatives, gross	629	343
Total assets	22,260	8,749
Liabilities
Derivatives, gross	702	440
Total derivatives	702	440
Fair Value, Inputs, Level 1 [Member]
Investment securities:
Equity securities	80	77
Debt securities	0	0
Derivatives, gross	0	0
Total assets	80	77
Liabilities
Derivatives, gross	0	0
Total derivatives	0	0
Fair Value, Inputs, Level 2 [Member]
Investment securities:
Equity securities	1	1
Debt securities	21,550	8,328
Derivatives, gross	629	343
Total assets	22,180	8,672
Liabilities
Derivatives, gross	702	440
Total derivatives	702	440
Fair Value, Inputs, Level 3 [Member]
Investment securities:
Equity securities	0	0
Debt securities	0	0
Derivatives, gross	0	0
Total assets	0	0
Liabilities
Derivatives, gross	0	0
Total derivatives	$ 0	$ 0