Stockholders' Equity (Details) - USD ($) $ in Thousands		1 Months Ended			3 Months Ended
	Mar. 03, 2020	Mar. 31, 2020	Nov. 30, 2019	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Subsidiary or Equity Method Investee [Line Items]
Repayments of debt in cash					$ 150,054	$ 493,355
Shares issued to settle convertible notes						182,435
Issuance costs			$ 400
Issuance of common stock for business combinations					$ 28,597	$ 0
Issuance of common stock for business combinations (in shares)		400,000	17,000,000.0		17,046,159
Merger Agreement with Genomic Health, Inc.
Subsidiary or Equity Method Investee [Line Items]
Business combination, consideration transferred			$ 2,500,000
Issuance of common stock for business combinations			$ 1,400,000
Paradigm & Viomics
Subsidiary or Equity Method Investee [Line Items]
Business combination, consideration transferred	$ 40,500
Issuance of common stock to acquire business	$ 32,200				$ 28,600
2025 Convertible notes
Subsidiary or Equity Method Investee [Line Items]
Settlement of convertible notes (in shares)				2,200,000
Shares issued to settle convertible notes				$ 182,400
Total consideration				676,500
Repayments of Debt				493,400
2027 Convertible notes | 2025 Convertible notes
Subsidiary or Equity Method Investee [Line Items]
Repayments of debt in cash				$ 494,100