Financial Instruments - Cash Flow Hedges Effect on Accumulated Other Comprehensive Earnings/(Losses), Net of Tax (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Balance at beginning of period	$ 27,351	$ 25,713
Transfer of realized losses/(gains) in fair value to earnings	104	29
Balance at end of period	25,752	25,909
Cash flow hedges
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Transfer of realized losses/(gains) in fair value to earnings	81	0
Unrealized (loss)/gain in fair value	(21)	(69)
Derivative Cash Flow Hedges
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net [Abstract]
Balance at beginning of period	(212)	(167)
Balance at end of period	$ (152)	$ (236)