Finance Arrangements - Interest Expense in Consolidated Income Statement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest Expense [Line Items]
Cash interest expense	$ 95	$ 75	$ 138	$ 157
Interest on convertible debentures	0	87	49	174
Accrual of notes payable final payment	8	32	39	64
Amortization of debt costs	12	7	19	14
Interest expense capital lease	0	1	0	2
Total interest expense	$ 115	$ 202	$ 245	$ 411