REVENUE RECOGNITION - Narrative (Details) $ in Thousands		1 Months Ended		3 Months Ended
	Sep. 30, 2019 USD ($) specific_radio_frequency	Sep. 30, 2020 USD ($)	Oct. 31, 2019 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Disaggregation of Revenue [Line Items]
Revenue from collaboration agreement				$ 608	$ 544
Proprietary Circuit Designs using XBAR Technology | Murata Manufacturing Co., Ltd.
Disaggregation of Revenue [Line Items]
Number of licensed specific radio frequencies | specific_radio_frequency	4
Prepaid royalties	$ 9,000
Written termination period	30 days
Contracted exclusivity period	30 months
Revenue from collaboration agreement		$ 2,500		$ 500	$ 500
Proprietary Circuit Designs using XBAR Technology | Accounts Receivable | Murata Manufacturing Co., Ltd.
Disaggregation of Revenue [Line Items]
Revenue from collaboration agreement			$ 2,000