Asset Quality (Financial Impact and TDRs by Concession Type) (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) loans	Dec. 31, 2014 USD ($) loans	Dec. 31, 2013 USD ($) loans
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	11,120	12,499	15,104
Pre-TDR Recorded Investment	$ 595,000,000	$ 707,000,000	$ 1,005,000,000
Post-TDR Recorded Investment	520,000,000	621,000,000	857,000,000
Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	22,000,000	37,000,000	38,000,000
Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	194,000,000	157,000,000	312,000,000
Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 304,000,000	$ 427,000,000	$ 507,000,000
Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	158	210	285
Pre-TDR Recorded Investment	$ 284,000,000	$ 363,000,000	$ 503,000,000
Post-TDR Recorded Investment	224,000,000	296,000,000	386,000,000
Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	22,000,000	37,000,000	38,000,000
Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	4,000,000	22,000,000	72,000,000
Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 198,000,000	$ 237,000,000	$ 276,000,000
Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	10,962	12,289	14,819
Pre-TDR Recorded Investment	$ 311,000,000	$ 344,000,000	$ 502,000,000
Post-TDR Recorded Investment	296,000,000	325,000,000	471,000,000
Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	190,000,000	135,000,000	240,000,000
Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 106,000,000	$ 190,000,000	$ 231,000,000
Commercial [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	130	131	168
Pre-TDR Recorded Investment	$ 246,000,000	$ 192,000,000	$ 216,000,000
Post-TDR Recorded Investment	204,000,000	158,000,000	163,000,000
Commercial [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	15,000,000	10,000,000	10,000,000
Commercial [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	3,000,000	11,000,000	21,000,000
Commercial [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 186,000,000	$ 137,000,000	$ 132,000,000
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	27	79	116
Pre-TDR Recorded Investment	$ 37,000,000	$ 171,000,000	$ 284,000,000
Post-TDR Recorded Investment	19,000,000	138,000,000	223,000,000
Commercial Real Estate [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	6,000,000	27,000,000	28,000,000
Commercial Real Estate [Member] | Total commercial lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	1,000,000	11,000,000	51,000,000
Commercial Real Estate [Member] | Total commercial lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 12,000,000	$ 100,000,000	$ 144,000,000
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	1		1
Pre-TDR Recorded Investment	$ 1,000,000		$ 3,000,000
Post-TDR Recorded Investment	1,000,000
Equipment Lease Financing [Member] | Total commercial lending [Member] | Principal Forgiveness [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 1,000,000
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	2,890	2,950	4,132
Pre-TDR Recorded Investment	$ 182,000,000	$ 193,000,000	$ 289,000,000
Post-TDR Recorded Investment	173,000,000	183,000,000	265,000,000
Home Equity [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	100,000,000	51,000,000	139,000,000
Home Equity [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 73,000,000	$ 132,000,000	$ 126,000,000
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	530	527	911
Pre-TDR Recorded Investment	$ 61,000,000	$ 73,000,000	$ 127,000,000
Post-TDR Recorded Investment	61,000,000	71,000,000	125,000,000
Residential Real Estate [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	36,000,000	26,000,000	39,000,000
Residential Real Estate [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 25,000,000	$ 45,000,000	$ 86,000,000
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	6,549	7,720	8,397
Pre-TDR Recorded Investment	$ 53,000,000	$ 60,000,000	$ 64,000,000
Post-TDR Recorded Investment	52,000,000	57,000,000	61,000,000
Credit Card [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 52,000,000	$ 57,000,000	$ 61,000,000
Other Consumer [Member] | Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loans	993	1,092	1,379
Pre-TDR Recorded Investment	$ 15,000,000	$ 18,000,000	$ 22,000,000
Post-TDR Recorded Investment	10,000,000	14,000,000	20,000,000
Other Consumer [Member] | Total consumer lending [Member] | Rate Reduction [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	2,000,000	1,000,000	1,000,000
Other Consumer [Member] | Total consumer lending [Member] | Other [Member]
Financing Receivable, Modifications [Line Items]
Post-TDR Recorded Investment	$ 8,000,000	$ 13,000,000	$ 19,000,000