Derivative gain (loss) recognized/reclassified (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 26	$ (2)	$ 35	$ (7)
Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), Adjustments, before Tax	15	0	18	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2)	(1)	(4)	(2)
Derivative Instrument, Noninterest Income (Expense)	6	9	12	24
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	0	0
Derivatives Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	26	(2)	35	(7)
Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), Adjustments, before Tax	15	0	18	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2)	(1)	(4)	(2)
Derivative Instrument, Noninterest Income (Expense)	0	0	0	0
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	0	0
Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Floor [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	2	0	2	0
Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), Adjustments, before Tax	15	0	18	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	0	(1)	0
Derivative Instrument, Noninterest Income (Expense)	0	0	0	0
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	0	0
Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	24	(2)	33	(7)
Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), Adjustments, before Tax	0	0	0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(1)	(3)	(2)
Derivative Instrument, Noninterest Income (Expense)	0	0	0	0
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	0	0
Derivatives Designated As Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	0	0
Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), Adjustments, before Tax	0	0	0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0	0
Derivative Instrument, Noninterest Income (Expense)	0	0	0	0
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	0	0	0	0
Derivatives Not Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Noninterest Income (Expense)	6	9	12	24
Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Noninterest Income (Expense)	6	5	11	10
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Noninterest Income (Expense)	(1)	0	(1)	0
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Noninterest Income (Expense)	86	(14)	132	(43)
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Noninterest Income (Expense)	$ (85)	$ 18	$ (130)	$ 57