Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investment securities:
Equity securities	$ 78	$ 48	$ 48
Debt securities	8,328	4,599
Derivatives, gross	343	514
Total assets	8,749	5,161
Liabilities
Derivatives, gross	440	214
Total derivatives	440	214
Fair Value, Inputs, Level 1 [Member]
Investment securities:
Equity securities	77	1
Debt securities	0	0
Derivatives, gross	0	0
Total assets	77	1
Liabilities
Derivatives, gross	0	0
Total derivatives	0	0
Fair Value, Inputs, Level 2 [Member]
Investment securities:
Equity securities	1	47
Debt securities	8,328	4,599
Derivatives, gross	343	514
Total assets	8,672	5,160
Liabilities
Derivatives, gross	440	214
Total derivatives	440	214
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