Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Deferred Tax Assets: Net Operating Loss Carryforwards	$ 184	$ 344
Deferred Tax Assets: Stock-Based Compensation	113	163
Deferred Tax Assets: Reserves and Accruals not Currently Deductible	423	426
Deferred Tax Assets, Intangible Assets	1,232	0
Deferred Tax Assets, upfront milestone payments	988	97
Deferred Tax Assets, Research and Other Credit Carryforwards	247	363
Deferred Tax Assets: Other, Net	168	183
Total Deferred Tax Assets Before Valuation Allowance	3,355	1,576
Valuation Allowance	(217)	(331)
Total Deferred Tax Assets	3,138	1,245
Deferred Tax Liabilities, Property, Plant and Equipment	(88)	(47)
Deferred Tax Liabilities, Intangible Assets	1,401	1,656
Deferred Tax Liabilities, Other	(93)	(80)
Deferred Tax Liabilities, Gross	(1,582)	(1,783)
Net deferred tax assets (liabilities)	$ 1,556
Net deferred tax assets (liabilities)		$ (538)