Derivative Instruments and Hedging Activities (Notional and Recorded Fair Values) (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Notional amount	$ 17,044,000,000	$ 15,030,000,000
Derivative asset, fair value	467,000,000	153,000,000
Derivative liability, fair value	36,000,000	19,000,000
Net credit valuation adjustment reducing fair value	26,000,000	11,000,000
Other assets
Derivative [Line Items]
Derivative asset, fair value	467,000,000	158,000,000
Other liabilities
Derivative [Line Items]
Derivative liability, fair value	471,000,000	167,000,000
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional amount	4,015,000,000	5,088,000,000
Designated as Hedging Instrument [Member] \| Other assets
Derivative [Line Items]
Derivative asset, fair value	0	0
Designated as Hedging Instrument [Member] \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	0	0
Designated as Hedging Instrument [Member] \| Purchased interest rate floors \| Cash Flow Hedging
Derivative [Line Items]
Derivative, Notional amount	0	0
Designated as Hedging Instrument [Member] \| Purchased interest rate floors \| Other assets \| Cash Flow Hedging
Derivative [Line Items]
Derivative asset, fair value	0	0
Designated as Hedging Instrument [Member] \| Purchased interest rate floors \| Other liabilities \| Cash Flow Hedging
Derivative [Line Items]
Derivative liability, fair value	0	0
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Cash Flow Hedging
Derivative [Line Items]
Derivative, Notional amount	3,200,000,000	3,588,000,000
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Fair Value Hedging
Derivative [Line Items]
Derivative, Notional amount	500,000,000	1,500,000,000
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Other assets \| Cash Flow Hedging
Derivative [Line Items]
Derivative asset, fair value	0	0
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Other assets \| Fair Value Hedging
Derivative [Line Items]
Derivative asset, fair value	0	0
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Other liabilities \| Cash Flow Hedging
Derivative [Line Items]
Derivative liability, fair value	0	0
Designated as Hedging Instrument [Member] \| Interest rate swaps \| Other liabilities \| Fair Value Hedging
Derivative [Line Items]
Derivative liability, fair value	0	0
Designated as Hedging Instrument [Member] \| Asset hedges: Pay-fixed interest rate swaps \| Fair Value Hedging
Derivative [Line Items]
Derivative, Notional amount	315,000,000
Designated as Hedging Instrument [Member] \| Asset hedges: Pay-fixed interest rate swaps \| Other assets \| Fair Value Hedging
Derivative [Line Items]
Derivative asset, fair value	0
Designated as Hedging Instrument [Member] \| Asset hedges: Pay-fixed interest rate swaps \| Other liabilities \| Fair Value Hedging
Derivative [Line Items]
Derivative liability, fair value	0
Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative, Notional amount	13,029,000,000	9,942,000,000
Derivatives not designated as hedging instruments \| Other assets
Derivative [Line Items]
Derivative asset, fair value	467,000,000	158,000,000
Derivatives not designated as hedging instruments \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	471,000,000	167,000,000
Derivatives not designated as hedging instruments \| Customer-facing interest rate derivatives
Derivative [Line Items]
Derivative, Notional amount	5,529,000,000	4,409,000,000
Derivatives not designated as hedging instruments \| Customer-facing interest rate derivatives \| Other assets
Derivative [Line Items]
Derivative asset, fair value	439,000,000	146,000,000
Derivatives not designated as hedging instruments \| Customer-facing interest rate derivatives \| Other assets \| Fair Value Hedging
Derivative [Line Items]
Derivative asset, fair value	439,000,000	141,000,000
Derivatives not designated as hedging instruments \| Customer-facing interest rate derivatives \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	0	5,000,000
Derivatives not designated as hedging instruments \| Customer-facing interest rate derivatives \| Other liabilities \| Fair Value Hedging
Derivative [Line Items]
Derivative liability, fair value	0	5,000,000
Derivatives not designated as hedging instruments \| Offsetting interest rate derivatives
Derivative [Line Items]
Derivative, Notional amount	5,530,000,000	4,422,000,000
Derivatives not designated as hedging instruments \| Offsetting interest rate derivatives \| Other assets
Derivative [Line Items]
Derivative asset, fair value	0	5,000,000
Derivatives not designated as hedging instruments \| Offsetting interest rate derivatives \| Other assets \| Fair Value Hedging
Derivative [Line Items]
Derivative asset, fair value	0	5,000,000
Derivatives not designated as hedging instruments \| Offsetting interest rate derivatives \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	465,000,000	157,000,000
Derivatives not designated as hedging instruments \| Offsetting interest rate derivatives \| Other liabilities \| Fair Value Hedging
Derivative [Line Items]
Derivative liability, fair value	30,000,000	9,000,000
Derivatives not designated as hedging instruments \| Other interest rate derivatives
Derivative [Line Items]
Derivative, Notional amount	1,766,000,000	726,000,000
Derivatives not designated as hedging instruments \| Other interest rate derivatives \| Other assets
Derivative [Line Items]
Derivative asset, fair value	25,000,000	3,000,000
Derivatives not designated as hedging instruments \| Other interest rate derivatives \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	4,000,000	1,000,000
Derivatives not designated as hedging instruments \| Foreign exchange derivatives
Derivative [Line Items]
Derivative, Notional amount	204,000,000	385,000,000
Derivatives not designated as hedging instruments \| Foreign exchange derivatives \| Other assets
Derivative [Line Items]
Derivative asset, fair value	3,000,000	4,000,000
Derivatives not designated as hedging instruments \| Foreign exchange derivatives \| Other liabilities
Derivative [Line Items]
Derivative liability, fair value	$ 2,000,000	$ 4,000,000

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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