NET LOSS PER SHARE - Anti-dilutive Shares Excluded From Calculation of Diluted Net Loss Per (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share	16,242	17,445
Options to purchase common stock, restricted stock units, and performance-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share	8,947	10,199
Shares issuable pursuant to employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share	152	103
Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares excluded from net loss per share	7,143	7,143