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Financial Instruments and Fair Value Measurements - Summary of Cash and Available-for-Sale Securities by Significant Investment Category (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 2,618,345 | $ 1,024,106
Level 2 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,242,194 | 1,259,980
Unrealized Gains | 4,413 | 3,047
Unrealized Losses | (151) | (40)
Fair Value | 5,246,456 | 1,262,987
Level 2 | Cash and Cash Equivalents |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 2,623,850 | 235,876
Level 2 | Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 1,983,758 | 867,124
Level 2 | Non- Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 638,848 | 159,987
Cash and Cash Equivalents | Level 1 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,623,849 | 225,874
Unrealized Gains | 1 | 0
Unrealized Losses | 0 | 0
Fair Value | 2,623,850 | 225,874
Cash and Cash Equivalents | Level 1 | Cash and Cash Equivalents |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 2,623,850 | 225,874
Cash and Cash Equivalents | Level 1 | Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 0
Cash and Cash Equivalents | Level 1 | Non- Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 0
Certificates of deposit | Level 2 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 238,774 | 82,028
Unrealized Gains | 49 | 79
Unrealized Losses | (4) | (6)
Fair Value | 238,819 | 82,101
Certificates of deposit | Level 2 | Cash and Cash Equivalents |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 10,002
Certificates of deposit | Level 2 | Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 215,389 | 69,197
Certificates of deposit | Level 2 | Non- Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 23,430 | 2,902
U.S. treasury securities | Level 2 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 491,549 | 117,891
Unrealized Gains | 69 | 260
Unrealized Losses | 0 | (2)
Fair Value | 491,618 | 118,149
U.S. treasury securities | Level 2 | Cash and Cash Equivalents |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 0
U.S. treasury securities | Level 2 | Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 491,618 | 110,186
U.S. treasury securities | Level 2 | Non- Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 7,963
Debt securities of U.S. government agencies and corporate entities | Level 2 |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,888,022 | 834,187
Unrealized Gains | 4,294 | 2,708
Unrealized Losses | (147) | (32)
Fair Value | 1,892,169 | 836,863
Debt securities of U.S. government agencies and corporate entities | Level 2 | Cash and Cash Equivalents |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 0 | 0
Debt securities of U.S. government agencies and corporate entities | Level 2 | Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | 1,276,751 | 687,741
Debt securities of U.S. government agencies and corporate entities | Level 2 | Non- Current Marketable Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Fair Value | $ 615,418 | $ 149,122

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