Asset Quality (Financial Impact and TDRs by Concession Type) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) loans	Sep. 30, 2014 USD ($) loans	Sep. 30, 2015 USD ($) loans	Sep. 30, 2014 USD ($) loans
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	3,053	3,322	8,514	8,956
Pre-TDR Recorded Investment	$ 175	$ 206	$ 435	$ 544
Post-TDR Recorded Investment	152	180	383	488
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	15	4	20	26
Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	62	44	154	120
Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 75	$ 132	$ 209	$ 342
Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	39	54	114	163
Pre-TDR Recorded Investment	$ 80	$ 102	$ 185	$ 272
Post-TDR Recorded Investment	62	81	144	232
Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	15	4	20	26
Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment		9	4	17
Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 47	$ 68	$ 120	$ 189
Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	3,014	3,268	8,400	8,793
Pre-TDR Recorded Investment	$ 95	$ 104	$ 250	$ 272
Post-TDR Recorded Investment	90	99	239	256
Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	62	35	150	103
Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 28	$ 64	$ 89	$ 153
Commercial [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	33	35	90	98
Pre-TDR Recorded Investment	$ 63	$ 39	$ 154	$ 128
Post-TDR Recorded Investment	52	24	129	109
Commercial [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	9	2	14	5
Commercial [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment		8	3	12
Commercial [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 43	$ 14	$ 112	$ 92
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	6	19	23	65
Pre-TDR Recorded Investment	$ 17	$ 63	$ 31	$ 144
Post-TDR Recorded Investment	10	57	15	123
Commercial Real Estate [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	6	2	6	21
Commercial Real Estate [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment		1	1	5
Commercial Real Estate [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 4	$ 54	$ 8	$ 97
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans			1
Pre-TDR Recorded Investment			$ 0
Post-TDR Recorded Investment			$ 0
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	788	942	2,318	2,334
Pre-TDR Recorded Investment	$ 42	$ 66	$ 144	$ 158
Post-TDR Recorded Investment	40	64	137	149
Home Equity [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	27	12	77	41
Home Equity [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 13	$ 52	$ 60	$ 108
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	329	159	477	439
Pre-TDR Recorded Investment	$ 35	$ 18	$ 55	$ 58
Post-TDR Recorded Investment	34	16	55	56
Residential Real Estate [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	21	8	32	21
Residential Real Estate [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 13	$ 8	$ 23	$ 35
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	1,651	1,860	4,855	5,226
Pre-TDR Recorded Investment	$ 14	$ 15	$ 40	$ 43
Post-TDR Recorded Investment	14	15	39	41
Credit Card [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 14	$ 15	$ 39	$ 41
Other Consumer [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	246	307	750	794
Pre-TDR Recorded Investment	$ 4	$ 5	$ 11	$ 13
Post-TDR Recorded Investment	2	4	8	10
Other Consumer [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment			2
Other Consumer [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 2	$ 4	$ 6	$ 10