STOCKHOLDERS' EQUITY (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Mar. 31, 2020	Nov. 30, 2019	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Subsidiary or Equity Method Investee [Line Items]
Repayments of debt in cash						$ 150,054	$ 493,356
Shares issued to settle convertible notes					$ 182,435
Issuance costs		$ 400
Issuance of common stock for business combinations				$ 28,597		$ 28,597	$ 0
Issuance of common stock for business combinations (in shares)	400,000	17,000,000.0				382,947
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	$ 28,600					$ 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