Asset Quality (Financial Impact and TDRs by Concession Type) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 loans	Dec. 31, 2013 loans	Dec. 31, 2012 loans
Financing Receivable, Modifications [Line Items]
Number of Loans	12,499	15,104	19,997
Pre-TDR Recorded Investment	$ 707	$ 1,005	$ 1,153
Post-TDR Recorded Investment	621	857	1,065
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	37	38	38
Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	157	312	487
Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	427	507	540
Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	210	285	289
Pre-TDR Recorded Investment	363	503	580
Post-TDR Recorded Investment	296	386	501
Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	37	38	38
Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	22	72	135
Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	237	276	328
Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	12,289	14,819	19,708
Pre-TDR Recorded Investment	344	502	573
Post-TDR Recorded Investment	325	471	564
Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	135	240	352
Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	190	231	212
Commercial [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	131	168	220
Pre-TDR Recorded Investment	192	216	335
Post-TDR Recorded Investment	158	163	283
Commercial [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	10	10	19
Commercial [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	11	21	58
Commercial [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	137	132	206
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	79	116	68
Pre-TDR Recorded Investment	171	284	244
Post-TDR Recorded Investment	138	223	217
Commercial Real Estate [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	27	28	19
Commercial Real Estate [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	11	51	77
Commercial Real Estate [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	100	144	121
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans		1	1
Pre-TDR Recorded Investment		3	1
Post-TDR Recorded Investment			1
Equipment Lease Financing [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment			1
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,950	4,132	4,813
Pre-TDR Recorded Investment	193	289	313
Post-TDR Recorded Investment	183	265	310
Home Equity [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	51	139	200
Home Equity [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	132	126	110
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	527	911	754
Pre-TDR Recorded Investment	73	127	147
Post-TDR Recorded Investment	71	125	143
Residential Real Estate [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	26	39	60
Residential Real Estate [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	45	86	83
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	7,720	8,397	13,306
Pre-TDR Recorded Investment	60	64	93
Post-TDR Recorded Investment	57	61	90
Credit Card [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	57	61	90
Other Consumer [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	1,092	1,379	835
Pre-TDR Recorded Investment	18	22	20
Post-TDR Recorded Investment	14	20	21
Other Consumer [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	1	1	2
Other Consumer [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 13	$ 19	$ 19