SEGMENT REPORTING, GEOGRAPHIC INFORMATION, AND SIGNIFICANT CUSTOMERS - Summary of Revenues by Geographic Revenue by Country (Detail) - Revenues - Geographic concentration risk	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Concentration risk	100.00%	100.00%
Korea
Concentration Risk [Line Items]
Concentration risk	49.00%	45.00%
United States of America
Concentration Risk [Line Items]
Concentration risk	16.00%	28.00%
Japan
Concentration Risk [Line Items]
Concentration risk	18.00%	17.00%
Other countries with less than 10% in a year
Concentration Risk [Line Items]
Concentration risk	17.00%	10.00%