Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Amount of (gain) loss reclassified from OCI into revenue	$ (1,373)	$ (1,220)	$ (1,160)	$ (1,123)	$ (1,371)	$ (1,296)	$ (1,345)	$ (1,237)	$ (4,876)	$ (5,249)	$ (5,207)
Other Comprehensive Income (Loss) | Foreign Exchange Contract
Derivative [Line Items]
Amount of gain (loss) recognized in OCI									9	(14)	(8)
Other Comprehensive Income (Loss) | Cross Currency Swaps
Derivative [Line Items]
Amount of gain (loss) recognized in OCI									(103)	22	22
Other Comprehensive Income (Loss) | Foreign Currency Denominated Debt
Derivative [Line Items]
Amount of gain (loss) recognized in OCI									(55)	13	27
Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign Exchange Contract
Derivative [Line Items]
Amount of (gain) loss reclassified from OCI into revenue									(4)	7	0
Amount of (gain) loss reclassified from OCI into cost of revenue									1	5	4
Interest Expense | Cross Currency Swaps
Derivative [Line Items]
Amount of gain (loss) recognized in OCI									$ 19	$ 16	$ 2