Litigation (Details)	1 Months Ended							12 Months Ended
	Jan. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2017 action	Jan. 31, 2017	Jan. 31, 2015 action	Dec. 31, 2013 USD ($)	Dec. 31, 2018 USD ($) defendant action	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Legal expense/(benefit)								$ 72,000,000	$ (35,000,000)	$ (317,000,000)
Threatened or Pending Litigation | Minimum
Loss Contingencies [Line Items]
Loss contingency range of possible loss								0
Threatened or Pending Litigation | Maximum
Loss Contingencies [Line Items]
Loss contingency range of possible loss								$ 1,500,000,000
Foreign Exchange Investigations and Litigation
Loss Contingencies [Line Items]
Loss contingency, exemption of disqualification period					5 years
Loss contingency disqualification period					10 years
Number of defendants | defendant								1
Number of actions dismissed | action						1
General Motors Litigation
Loss Contingencies [Line Items]
Syndicated term loan facility for General Motors Corporation								$ 1,500,000,000
Interchange Litigation
Loss Contingencies [Line Items]
Number of separate actions | action				2
Settlement amount		$ 36,000,000
Interchange Litigation | The Defendants
Loss Contingencies [Line Items]
Settlement amount		$ 900,000,000					$ 5,300,000,000
Interchange Litigation | Visa Defendants
Loss Contingencies [Line Items]
Amount deposited into litigation escrow account			$ 600,000,000
Interchange Litigation | Visa Defendants | Subsequent Event
Loss Contingencies [Line Items]
Settlement amount	$ 600,000,000
Interchange Litigation | Mastercard and Certain Banks | Subsequent Event
Loss Contingencies [Line Items]
Settlement amount	$ 300,000,000
LIBOR and Other Benchmark Rate Investigations and Litigation | Pending Litigation
Loss Contingencies [Line Items]
Number of putative class actions | action								2
Municipal Derivatives Litigation | Minimum
Loss Contingencies [Line Items]
Warrants the firm was chosen to underwrite based upon alleged payments made to certain third parties (more than)								$ 3,000,000,000.0