Asset Quality - Post-Modification Outstanding Recorded Investment by Concession Type for Our Commercial Accruing and Nonaccruing TDRs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Total commercial and consumer TDRs	$ 186	$ 130
Total loans	89,552	86,405
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Extension of maturity date	15	12
Payment or covenant modification/deferment	99	46
Bankruptcy plan modification	7	31
Total	121	89
Total loans	66,310	62,733
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Interest rate reduction	27	13
Forgiveness of principal	0	0
Other	38	28
Total	65	41
Total loans	$ 23,242	$ 23,672