Segment Information - Foreign and U.S. Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	$ 47,170	$ 40,580	$ 38,691
Revenues From External Customers [Member] | Geographic Concentration Risk [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration Risk, Benchmark Description	Consolidated revenues from external customers
Concentration Risk, Additional Characteristic	Single foreign country
Revenues From External Customers [Member] | Geographic Concentration Risk [Member] | Maximum [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration Risk, Percentage	5.00%
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	$ 42,773	36,555	35,011
South Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	2,093	1,892	1,666
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	$ 2,304	$ 2,133	$ 2,014