Derivative Instruments (Current Period Cash Flow Hedges in AOCI (loss) before Taxes) (Details) - Cash flow hedges in AOCI $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Balance, beginning	$ 832
Amount recorded in AOCI	2,742
Amount reclassified from AOCI to income	(388)
Balance, ending	3,186
Interest Rate
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount recorded in AOCI	51
Amount reclassified from AOCI to income	1
Currency
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount recorded in AOCI	103
Amount reclassified from AOCI to income	(1)
Currency/Interest Rate
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amount recorded in AOCI	2,588
Amount reclassified from AOCI to income	$ (388)