Loans - Contractual Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		$ 26,364
2017		8,094
2018		9,658
2019		11,159
2020		7,348
Thereafter		20,294
Total loans		82,917		$ 77,741	$ 67,695
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		62,453		58,087
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans		20,464		19,654
Construction and Other Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		3,892
2017		1,022
2018		1,436
2019		1,685
2020		1,090
Thereafter		875
Total loans		10,000		10,300	9,034
Business and Corporate Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		7,441
2017		1,954
2018		2,745
2019		3,220
2020		2,084
Thereafter		1,672
Total loans		19,116		17,819	14,446
Global Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		11,665
2017		3,064
2018		4,303
2019		5,048
2020		3,267
Thereafter		2,622
Total loans		29,969		26,387	21,625
Other Commercial [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		1,311
2017		344
2018		484
2019		567
2020		367
Thereafter		295
Total loans		3,368		3,581	3,389
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		1,349
2017		421
2018		426
2019		478
2020		441
Thereafter		14,643
Total loans		17,758		16,661	15,826
Home Equity Mortgages [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016	[1]	520
2017	[1]	372
2018	[1]	262
2019	[1]	160
2020	[1]	99
Thereafter	[1]	187
Total loans		1,600	[1]	1,784	2,011
Credit Cards [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016	[2]	0
2017	[2]	699
2018	[2]	0
2019	[2]	0
2020	[2]	0
Thereafter	[2]	0
Total loans		699	[2]	720	854
Other consumer | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
2016		186
2017		218
2018		2
2019		1
2020	[2]	0
Thereafter		0
Total loans		$ 407		$ 489	$ 510

[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.