Segment Information - Foreign and U.S. Revenues from External Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues from external customers	$ 159,157	$ 152,176	$ 47,170
United States
Disaggregation of Revenue [Line Items]
Revenues from external customers	154,042	147,332	42,773
South Korea
Disaggregation of Revenue [Line Items]
Revenues from external customers	2,123	2,022	2,093
All other foreign countries
Disaggregation of Revenue [Line Items]
Revenues from external customers	$ 2,992	$ 2,822	$ 2,304