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Derivatives and Hedging Activities (Impact of Hedging Activity) (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss)
Interest and debt expense	$ 214	$ 245	$ 207
Derivatives liabilities, credit risk related contingent features
Aggregate fair value of all derivative instruments containing credit risk features	189	171
Aggregate fair value of assets posted as collateral	189	170
Additional collateral required to be posted	0	1
Cash flow hedges [Member]
Derivative Instruments, Gain (Loss)
Estimated reclassification of net pretax losses on cash flow hedges from accumulated other comprehensive income to earnings during the next 12 months	$ (1)
Longest period of time over which the entity hedges exposure to the variability in future cash flows	16 years
Fair value hedges [Member]
Derivative Instruments, Gain (Loss)
Interest and debt expense	$ 214	245
Net investment hedges [Member]
Derivative Instruments, Gain (Loss)
Gain (loss) on net investment hedge recorded in OCI	2	14
Interest rate contracts [Member] \| Cash flow hedges [Member]
Derivative Instruments, Gain (Loss)
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net	2	0
Interest rate contracts [Member] \| Fair value hedges [Member]
Derivative Instruments, Gain (Loss)
Increase (Decrease) in Fair Value of Hedged Item in Interest Rate Fair Value Hedge	5	15
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments	$ (5)	$ (15)