Sale of Certain Private Banking Client Relationships (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Aug. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Client deposit		$ 118,702		$ 129,248	$ 118,579
Client investments transferred during the fourth quarter		500
Client deposits transferred during the fourth quarter		300
Client deposits held for sale		673		$ 0
Portion of Latin America Portfolio [Member] | PB [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Client investments	$ 3,500
Client deposit	$ 1,700
Fee, as percent of assets transferred during first 2 years of agreement (percent)	0.50%
Client deposits held for sale		700
Additional deposits conditionally eligible for transfer		400
Other assets [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Contingent consideration receivable		$ 15
Other Income (Loss) [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Pre-tax gain on sale			$ 8
Maximum [Member] | Other assets [Member]
Risks Inherent in Servicing Assets and Servicing Liabilities [Line Items]
Contingent consideration receivable			$ 26