MARKETABLE SECURITIES - Schedule of Underlying Maturities of AFS Securities (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Available-for-sale securities
Due in one year or less	$ 463,036
Due in one year or less	462,858
Due after one year through four years	191,088
Due after one year through four years	189,549
Cash equivalents
Available-for-sale securities
Due in one year or less	123,392
Due in one year or less	123,370
Cash equivalents | U.S. government agency securities
Available-for-sale securities
Due in one year or less	55,299
Due in one year or less	55,331
Cash equivalents | Commercial paper
Available-for-sale securities
Due in one year or less	19,955
Due in one year or less	19,950
Cash equivalents | Corporate bonds
Available-for-sale securities
Due in one year or less	39,443
Due in one year or less	39,396
Cash equivalents | Asset backed securities
Available-for-sale securities
Due in one year or less	8,695
Due in one year or less	8,693
Short-term Investments
Available-for-sale securities
Due in one year or less	339,644
Due in one year or less	339,488
Due after one year through four years	191,088
Due after one year through four years	189,549
Short-term Investments | U.S. government agency securities
Available-for-sale securities
Due in one year or less	175,419
Due in one year or less	175,992
Due after one year through four years	27,209
Due after one year through four years	27,258
Short-term Investments | Commercial paper
Available-for-sale securities
Due in one year or less	7,964
Due in one year or less	7,952
Due after one year through four years	0
Due after one year through four years	0
Short-term Investments | Certificates of deposit
Available-for-sale securities
Due in one year or less	20,000
Due in one year or less	19,973
Due after one year through four years	11,653
Due after one year through four years	11,546
Short-term Investments | Corporate bonds
Available-for-sale securities
Due in one year or less	129,321
Due in one year or less	128,624
Due after one year through four years	130,897
Due after one year through four years	129,497
Short-term Investments | Asset backed securities
Available-for-sale securities
Due in one year or less	6,940
Due in one year or less	6,947
Due after one year through four years	21,329
Due after one year through four years	$ 21,248