Fair Value Measurements Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Unrealized gain on investment of equity securities	$ 58	$ 168	$ 312	$ 149
Short-term and long-term debt	24,588		24,588		$ 27,322
Market value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term and long-term debt	27,200		27,200		27,100
Carrying value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Short-term and long-term debt	$ 24,600		$ 24,600		$ 27,300