Loans and ACL - Schedule of Performing and Nonperforming TDRs (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable [Line Items]
Total TDRs	$ 1,232	$ 1,371
ALLL attributable to TDRs	142	146
Performing TDRs
Financing Receivable [Line Items]
Total TDRs	1,043	1,187
Nonperforming TDRs (also included in NPL disclosures)
Financing Receivable [Line Items]
Total TDRs	189	184
Commercial | Performing TDRs | Commercial and industrial
Financing Receivable [Line Items]
Total TDRs	50	57
Commercial | Performing TDRs | CRE
Financing Receivable [Line Items]
Total TDRs	16	25
Commercial | Performing TDRs | Lease financing
Financing Receivable [Line Items]
Total TDRs	0	0
Retail | Performing TDRs | Residential mortgage
Financing Receivable [Line Items]
Total TDRs	605	769
Retail | Performing TDRs | Direct
Financing Receivable [Line Items]
Total TDRs	62	67
Retail | Performing TDRs | Indirect
Financing Receivable [Line Items]
Total TDRs	281	240
Revolving credit | Performing TDRs
Financing Receivable [Line Items]
Total TDRs	$ 29	$ 29