Credit Quality And Allowance For Credit Losses (Changes In The Allowance For Loan Losses And Related Loan Amounts) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for loan losses		$ 60	$ 26	$ 47	$ 14	$ 2	$ 5	$ 11	$ 9	$ 147	$ 27	$ 46
Total loans													$ 49,084	$ 48,593
Allowance for loan losses on PCI loans													$ 0	$ 0	$ 0
Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					594				598	594	598	629
Loan charge-offs										(168)	(102)	(153)
Recoveries on loans previously charged-off										68	77	80
Net loan (charge-offs) recoveries										(100)	(25)	(73)
Provision for loan losses										142	22	42
Foreign currency translation adjustment										(2)	(1)	0
Balance at end of period		634				594				634	594	598
Allowance for loan losses as a percentage of total loans													1.29%	1.22%	1.32%
Allowance for loan losses individually evaluated for impairment													$ 53	$ 39	$ 57
Allowance for loan losses collectively evaluated for impairment													581	555	541
Total allowance for loan losses		634			594	594			598	594	598	629	634	594	598
Loans individually evaluated for impairment													424	219	274
Loans collectively evaluated for impairment													48,659	48,372	45,191
PCI loans	[1]												1	2	5
Total loans													$ 49,084	$ 48,593	$ 45,470
Business loans | Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					534				531	534	531	552
Loan charge-offs										(157)	(87)	(130)
Recoveries on loans previously charged-off										55	68	70
Net loan (charge-offs) recoveries										(102)	(19)	(60)
Provision for loan losses										149	23	39
Foreign currency translation adjustment										(2)	(1)	0
Balance at end of period		579				534				579	534	531
Allowance for loan losses as a percentage of total loans													1.30%	1.20%	1.28%
Allowance for loan losses individually evaluated for impairment													$ 53	$ 39	$ 57
Allowance for loan losses collectively evaluated for impairment													526	495	474
Total allowance for loan losses		579			534	534			531	534	531	552	579	534	531
Loans individually evaluated for impairment													393	177	223
Loans collectively evaluated for impairment													44,336	44,203	41,311
PCI loans	[1]												0	0	2
Total loans													44,729	44,380	$ 41,536
Retail loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans													$ 4,355	$ 4,213
Retail loans | Financing Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period					60				67	60	67	77
Loan charge-offs										(11)	(15)	(23)
Recoveries on loans previously charged-off										13	9	10
Net loan (charge-offs) recoveries										2	(6)	(13)
Provision for loan losses										(7)	(1)	3
Foreign currency translation adjustment										0	0	0
Balance at end of period		55				60				55	60	67
Allowance for loan losses as a percentage of total loans													1.26%	1.43%	1.70%
Allowance for loan losses individually evaluated for impairment													$ 0	$ 0	$ 0
Allowance for loan losses collectively evaluated for impairment													55	60	67
Total allowance for loan losses		$ 55			$ 60	$ 60			$ 67	$ 60	$ 67	$ 77	55	60	67
Loans individually evaluated for impairment													31	42	51
Loans collectively evaluated for impairment													4,323	4,169	3,880
PCI loans	[1]												1	2	3
Total loans													$ 4,355	$ 4,213	$ 3,934

[1] No allowance for loan losses was required for PCI loans at December 31, 2015, 2014 and 2013.