Loans - Contractual Maturities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	$ 21,951
2016	8,573
2017	6,890
2018	10,005
2019	10,717
Thereafter	19,605
Total loans	77,741		67,695	63,258
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	58,087		48,494
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	19,654		19,201
Construction and Other Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	3,455
2016	1,205
2017	1,104
2018	1,673
2019	1,811
Thereafter	1,052
Total loans	10,300		9,034	8,457
Business and Corporate Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	5,977
2016	2,084
2017	1,910
2018	2,894
2019	3,133
Thereafter	1,821
Total loans	17,819		14,446	12,608
Global Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	8,851
2016	3,086
2017	2,829
2018	4,285
2019	4,640
Thereafter	2,696
Total loans	26,387		21,625	20,009
Other Commercial [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	1,200
2016	419
2017	384
2018	582
2019	630
Thereafter	366
Total loans	3,581		3,389	3,076
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	1,584
2016	401
2017	397
2018	411
2019	404
Thereafter	13,464
Total loans	16,661		15,826	15,371
Home Equity Mortgages [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	622	[1]
2016	435	[1]
2017	263	[1]
2018	160	[1]
2019	99	[1]
Thereafter	205	[1]
Total loans	1,784	[1]	2,011	2,324
Credit Cards [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	0	[2]
2016	720	[2]
2017	0	[2]
2018	0	[2]
2019	0	[2]
Thereafter	0	[2]
Total loans	720	[2]	854	815
Other consumer | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2015	262
2016	223
2017	3
2018	0
2019	0
Thereafter	1
Total loans	$ 489		$ 510	$ 598

[1] Home equity mortgage maturities reflect estimates based on historical payment patterns.

[2] As credit card receivables do not have stated maturities, the table reflects estimates based on historical payment patterns.