Fair Value Measurements - Financial Assets and Liabilities Subject to Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Cash	$ 1,800,000	$ 2,300,000
Financial instruments carried at fair value (liability positions):
Long-term contingent consideration	(178,100)	(176,500)
Recurring basis
Financial instruments carried at fair value (asset positions):
Derivative asset current	25,434	9,725
Derivative asset noncurrent	1,798
Total financial assets	2,391,829	1,535,278
Financial instruments carried at fair value (liability positions):
Derivative liability current	(459)	(5,533)
Long-term contingent consideration	(178,100)	(176,500)
Derivative liability, noncurrent	(637)	(1,821)
Total financial liabilities	(179,196)	(183,854)
Recurring basis \| Level 1
Financial instruments carried at fair value (asset positions):
Derivative asset current	0	0
Derivative asset noncurrent	0
Total financial assets	1,890,169	1,065,569
Financial instruments carried at fair value (liability positions):
Derivative liability current	0	0
Long-term contingent consideration	0	0
Derivative liability, noncurrent	0	0
Total financial liabilities	0	0
Recurring basis \| Level 2
Financial instruments carried at fair value (asset positions):
Derivative asset current	25,434	9,725
Derivative asset noncurrent	1,798
Total financial assets	501,660	469,709
Financial instruments carried at fair value (liability positions):
Derivative liability current	(459)	(5,533)
Long-term contingent consideration	0	0
Derivative liability, noncurrent	(637)	(1,821)
Total financial liabilities	(1,096)	(7,354)
Recurring basis \| Level 3
Financial instruments carried at fair value (asset positions):
Derivative asset current	0	0
Derivative asset noncurrent	0
Total financial assets	0	0
Financial instruments carried at fair value (liability positions):
Derivative liability current	0	0
Long-term contingent consideration	(178,100)	(176,500)
Derivative liability, noncurrent	0	0
Total financial liabilities	(178,100)	(176,500)
Recurring basis \| Money market funds
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	1,736,913	791,039
Recurring basis \| Money market funds \| Level 1
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	1,736,913	791,039
Recurring basis \| Money market funds \| Level 2
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	0	0
Recurring basis \| Money market funds \| Level 3
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	0	0
Recurring basis \| Government-sponsored enterprise securities
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents		6,070
Marketable securities	7,791	12,733
Recurring basis \| Government-sponsored enterprise securities \| Level 1
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents		0
Marketable securities	7,791	12,733
Recurring basis \| Government-sponsored enterprise securities \| Level 2
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents		6,070
Marketable securities	0	0
Recurring basis \| Government-sponsored enterprise securities \| Level 3
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents		0
Marketable securities	0	0
Recurring basis \| Commercial paper
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	30,700	29,472
Marketable securities	118,964	102,356
Recurring basis \| Commercial paper \| Level 1
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	0	0
Marketable securities	0	0
Recurring basis \| Commercial paper \| Level 2
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	30,700	29,472
Marketable securities	118,964	102,356
Recurring basis \| Commercial paper \| Level 3
Financial instruments carried at fair value (asset positions):
Cash and cash equivalents	0	0
Marketable securities	0	0
Recurring basis \| Corporate equity securities
Financial instruments carried at fair value (asset positions):
Marketable securities	165,178	282,084
Recurring basis \| Corporate equity securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities	145,465	261,797
Recurring basis \| Corporate equity securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities	19,713	20,287
Recurring basis \| Corporate equity securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities	0	0
Recurring basis \| Corporate debt securities
Financial instruments carried at fair value (asset positions):
Marketable securities	305,051	301,799
Recurring basis \| Corporate debt securities \| Level 1
Financial instruments carried at fair value (asset positions):
Marketable securities	0	0
Recurring basis \| Corporate debt securities \| Level 2
Financial instruments carried at fair value (asset positions):
Marketable securities	305,051	301,799
Recurring basis \| Corporate debt securities \| Level 3
Financial instruments carried at fair value (asset positions):
Marketable securities	$ 0	$ 0

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 liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of investment in marketable security.

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