STOCKHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended				9 Months Ended
	Mar. 31, 2020	Nov. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 01, 2020	Jun. 30, 2020	Dec. 31, 2019
Subsidiary or Equity Method Investee [Line Items]
Common stock, authorized shares (in shares)				400,000,000				400,000,000		400,000,000	200,000,000	400,000,000
Repayments of debt in cash								$ 150,054	$ 493,356
Settlement of convertible notes (in shares)						26
Shares issued to settle convertible notes							$ 182,435
Issuance costs		$ 400				$ 409
Issuance of common stock for business combinations				$ 250	$ 28,597			$ 28,847	$ 0
Issuance of common stock for business combinations (in shares)	400,000	17,000,000.0						386,293
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	$ 40,400
Issuance of common stock to acquire business	$ 28,800							$ 32,200
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
Subsidiary or Equity Method Investee [Line Items]
Repayments of debt in cash			494,100
Shares issued to settle convertible notes			182,400
Total consideration			676,500
2027 Convertible notes | 2025 Convertible notes
Subsidiary or Equity Method Investee [Line Items]
Repayments of debt in cash			$ 494,100