Allowance for Loan and Lease Losses Allowance for Loan and Lease Losses - Loss Sharing Arrangements (Details) - Loss sharing agreements - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Expected reimbursement from loss sharing partners, beginning balance	$ 414	$ 392	$ 379	$ 380
Amounts due from partners which reduced net charge-offs	(100)	(97)	(313)	(286)
Amounts estimated to be charged to partners which reduced provision for credit losses	86	81	334	282
Expected reimbursement from loss sharing partners, ending balance	$ 400	$ 376	$ 400	$ 376