Fair Value Measurements Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain on investment of equity securities	$ 57		$ 254
Unrealized loss on investment of equity securities		$ 64		$ 19
Short-term and long-term debt	26,083		26,083		$ 27,322
Market value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term and long-term debt	28,000		28,000		27,100
Carrying value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term and long-term debt	$ 26,100		$ 26,100		$ 27,300