Derivative Financial Instruments Derivative Financial Instruments - Carrying Value of Hedged Items in Fair Value Hedge (Details) $ in Millions	Dec. 31, 2019 USD ($)
Securities available-for-sale [Member]
Derivatives, Fair Value [Line Items]
Carrying amount of hedged asset items	$ 7,277	[1]
Active hedged asset adjustments	554
Discontinued hedged asset adjustments	428
Total hedged asset adjustments	982
Long-term Debt [Member]
Derivatives, Fair Value [Line Items]
Carrying amount of hedged liability items	10,975	[1]
Active hedged liability adjustments	285
Discontinued hedged liability adjustments	(32)
Total hedged liability adjustments	$ 253

[1] The carrying amount of securities AFS represents the amortized cost basis.