DEBT SECURITIES - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 5,015	$ 79,151
Less Than 12 Months, Unrealized Losses	9	65
12 Months or Greater, Fair Value	0	7,509
12 Months or Greater, Unrealized Losses	0	2
Total, Fair Value	5,015	86,660
Total, Unrealized Losses	9	67
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	0
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	0
Total, Unrealized Losses	0	0
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	5,015	74,151
Less Than 12 Months, Unrealized Losses	9	64
12 Months or Greater, Fair Value	0	7,509
12 Months or Greater, Unrealized Losses	0	2
Total, Fair Value	5,015	81,660
Total, Unrealized Losses	9	66
Securities of government-sponsored entities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	5,000
Less Than 12 Months, Unrealized Losses	0	1
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Unrealized Losses	0	0
Total, Fair Value	0	5,000
Total, Unrealized Losses	$ 0	$ 1