Loans and Allowance for Loan Losses - Sale Of Loans Held-For-Sale (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost Derecognized	$ 1,295
Valuation Allowance Derecognized	0
Proceeds from Sale	1,305
Gain (Loss) on Sales	11
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost Derecognized	751
Valuation Allowance Derecognized	0
Proceeds from Sale	752
Gain (Loss) on Sales	3
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized Cost Derecognized	544
Valuation Allowance Derecognized	0
Proceeds from Sale	553
Gain (Loss) on Sales	$ 8