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Derivatives and Hedging Activities (Impact of Hedging Activity) (Details 4) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss)
Interest and debt expense	$ 53	$ 51
Derivative, Credit Risk Related Contingent Features [Abstract]
Aggregate fair value of derivative contracts in a net liability position containing such credit contingent instruments	273		$ 171
Aggregate fair value of assets posted as collateral for such instruments	272		$ 170
Aggregate fair value of additional assets required to be posted or needed to settle the instruments	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	$ 53	51
Net investment hedges [Member]
Derivative Instruments, Gain (Loss)
Gain (loss) on net investment hedge	3	7
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	1	8
Derivative, Credit Risk Related Contingent Features [Abstract]
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments	$ (1)	$ (8)