Financing Arrangements - Interest Expense in Consolidated Income Statement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest Expense [Line Items]
Cash interest expense	$ 92	$ 43
Interest on convertible debentures		49
Accrual of notes payable final payment	7	31
Amortization of debt costs	13	7
Total interest expense	$ 112	$ 130