Collaborations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues	$ 5,904	$ 5,773	$ 17,517	$ 17,047
Other revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues	394	320	985	821
Collaborative arrangement with Novartis Pharma AG [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payment	100		100
Collaborative arrangement with Novartis Pharma AG [Member] | Other revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues	$ 147	$ 60	$ 295	$ 60