Investments and Fair Value Measurement - Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financial Assets
Non-marketable debt securities	$ 2,955	$ 2,370
Total financial assets	8,157	3,875
Financial Liabilities
Other	0	9
Warrants	0	52
Embedded derivatives	0	2,018
Total financial liabilities	0	2,079
Money market funds
Financial Assets
Cash and cash equivalents	5,104	1,505
Commercial paper
Financial Assets
Non-marketable debt securities	233	0
U.S. government and agency securities
Financial Assets
Non-marketable debt securities	153	0
Corporate bonds
Financial Assets
Non-marketable debt securities	199	0
Corporate Debt Securities
Financial Assets
Non-marketable debt securities	2,370	2,370
Non-marketable equity securities
Financial Assets
Non-marketable equity securities	98	0
Level 1
Financial Assets
Total financial assets	5,104	1,505
Financial Liabilities
Other	0	0
Warrants	0	0
Embedded derivatives	0	0
Total financial liabilities	0	0
Level 1 \| Money market funds
Financial Assets
Cash and cash equivalents	5,104	1,505
Level 1 \| Commercial paper
Financial Assets
Non-marketable debt securities	0	0
Level 1 \| U.S. government and agency securities
Financial Assets
Non-marketable debt securities	0	0
Level 1 \| Corporate bonds
Financial Assets
Non-marketable debt securities	0	0
Level 1 \| Corporate Debt Securities
Financial Assets
Non-marketable debt securities	0	0
Level 1 \| Non-marketable equity securities
Financial Assets
Non-marketable equity securities	0	0
Level 2
Financial Assets
Total financial assets	585	0
Financial Liabilities
Other	0	0
Warrants	0	0
Embedded derivatives	0	0
Total financial liabilities	0	0
Level 2 \| Money market funds
Financial Assets
Cash and cash equivalents	0	0
Level 2 \| Commercial paper
Financial Assets
Non-marketable debt securities	233	0
Level 2 \| U.S. government and agency securities
Financial Assets
Non-marketable debt securities	153	0
Level 2 \| Corporate bonds
Financial Assets
Non-marketable debt securities	199	0
Level 2 \| Corporate Debt Securities
Financial Assets
Non-marketable debt securities	0	0
Level 2 \| Non-marketable equity securities
Financial Assets
Non-marketable equity securities	0	0
Level 3
Financial Assets
Total financial assets	2,468	2,370
Financial Liabilities
Other	0	9
Warrants	0	52
Embedded derivatives	0	2,018
Total financial liabilities	0	2,079
Level 3 \| Money market funds
Financial Assets
Cash and cash equivalents	0	0
Level 3 \| Commercial paper
Financial Assets
Non-marketable debt securities	0	0
Level 3 \| U.S. government and agency securities
Financial Assets
Non-marketable debt securities	0	0
Level 3 \| Corporate bonds
Financial Assets
Non-marketable debt securities	0	0
Level 3 \| Corporate Debt Securities
Financial Assets
Non-marketable debt securities	2,370	2,370
Level 3 \| Non-marketable equity securities
Financial Assets
Non-marketable equity securities	$ 98	$ 0

Fair value portion of accrued expenses.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

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