Litigation (Details)	1 Months Ended					3 Months Ended		5 Months Ended	9 Months Ended		36 Months Ended
	Sep. 30, 2018 USD ($)	Nov. 30, 2017 USD ($)	Mar. 31, 2017 action	Jan. 31, 2017	Dec. 31, 2013 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) action	Sep. 30, 2018 USD ($)	Dec. 31, 2013 USD ($)
Loss Contingencies [Line Items]
Legal expense/(benefit)						$ 10,000,000	$ 20,000,000		$ (2,000,000)	$ 90,000,000
Threatened or Pending Litigation | Minimum
Loss Contingencies [Line Items]
Loss contingency range of possible loss						0		$ 0	0
Threatened or Pending Litigation | Maximum
Loss Contingencies [Line Items]
Loss contingency range of possible loss						$ 1,300,000,000		1,300,000,000	$ 1,300,000,000
Federal Republic of Nigeria Litigation | Federal Government of Nigeria and Two Major International Oil Companies
Loss Contingencies [Line Items]
Amount paid out of monies in account following settlement of dispute											$ 1,100,000,000
Federal Republic of Nigeria Litigation | Federal Republic of Nigeria
Loss Contingencies [Line Items]
Amount of claim		$ 875,000,000
Foreign Exchange Investigations and Litigation
Loss Contingencies [Line Items]
Exemption of disqualification period				5 years
Disqualification period				10 years
Payments for fines in connection with legal settlement								$ 265,000,000
Number of actions dismissed | action									2
Interchange Litigation
Loss Contingencies [Line Items]
Number of separate actions | action			2
Interchange Litigation | The Defendants
Loss Contingencies [Line Items]
Settlement amount	$ 900,000,000				$ 5,300,000,000