Financial Instruments - Total Short-Term and Long-Term Investments (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Financial Instruments [Abstract]
Equity securities		$ 4,753	$ 1,600
Available-for-sale debt securities		5,027	15,091
Held-to-maturity debt securities		1,347	1,003
Total Short-term investments	[1]	11,128	17,694
Equity securities		1,425	1,223
Trading equity funds securities		53	50
Available-for-sale debt securities		430	491
Held-to-maturity debt securities		47	59
Private equity investments at cost, as adjusted, or equity method		951	944
Total Long-term investments	[1]	2,905	2,767
Held-to-maturity cash equivalents		$ 163	$ 199

[1] Amounts may not add due to rounding.