Notional and Recorded Fair Values (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 210	$ 75
Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	223	76
Other Debt Obligations [Member]
Derivative [Line Items]
Derivative, Notional Amount	13,677	7,528
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	4,613	1,187
Designated as Hedging Instrument [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Designated as Hedging Instrument [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	0	0
Designated as Hedging Instrument [Member] | Interest Rate Floor [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	0	0
Designated as Hedging Instrument [Member] | Interest Rate Floor [Member] | Other Assets [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Designated as Hedging Instrument [Member] | Interest Rate Floor [Member] | Other Liabilities [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,613	687
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,000	500
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Assets [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Assets [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Liabilities [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Liabilities [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	0	0
Derivatives Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Derivative, Notional Amount	9,064	6,341
Derivatives Not Designated As Hedging Instruments [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	210	75
Derivatives Not Designated As Hedging Instruments [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	223	76
Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member]
Derivative [Line Items]
Derivative, Notional Amount	298	389
Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3	4
Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	2	2
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	812	300
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	4	1
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	1	1
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,974	2,826
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	33
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member] | Other Assets [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	33
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	220	40
Derivatives Not Designated As Hedging Instruments [Member] | Offsetting Interest Rate Derivatives [Member] | Other Liabilities [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	13	3
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,980	2,826
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	203	37
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member] | Other Assets [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	203	7
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member] | Other Liabilities [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	0	33
Derivatives Not Designated As Hedging Instruments [Member] | Interest Rate Swaps For Customers [Member] | Other Liabilities [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivatives hedging instruments, liabilities	$ 0	$ 33