Fair value measurements Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain on investment of equity securities			$ 1,200,000,000	$ 115,000,000
Short-term and long-term deb	$ 24,593,000,000	$ 27,322,000,000	24,593,000,000	27,322,000,000
In-process research and development impairment	800,000,000	820,000,000	800,000,000	820,000,000	$ 0
Fair value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term and long-term debt	27,300,000,000	27,100,000,000	27,300,000,000	27,100,000,000
Fair Value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term and long-term deb	$ 24,600,000,000	27,300,000,000	$ 24,600,000,000	27,300,000,000
Kite 585 Program [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)		$ 0		$ 0