Acquisition, Divestitures, Licensing Arrangements, Collaborative Arrangements and Privately Held Investment - Licensing Arrangement (Details) - Licensing Arrangement [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Apr. 01, 2018	Sep. 30, 2018	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from licensing arrangement				$ 40
Shire [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from licensing arrangement		$ 35	$ 75	$ 110
Maximum amount of possible development and sales-based milestone payments and potential future royalty payments					$ 460
BionTech [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum amount of possible development and sales-based milestone payments and potential future royalty payments	$ 325
Other (Income)/Deductions, Net [Member] | Shire [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from licensing arrangement			$ 75		$ 90
Research and Development Expense [Member] | BionTech [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment for licensing arrangement	$ 50
Long-term Investments [Member] | BionTech [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares purchased (in shares)		169,670
Value of shares purchased		$ 50