Intangibles - Amortization of Intangible Assets Acquired (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Capitalized patent costs	$ 10,082	$ 9,708
Intangible assets acquired:
Gross intangible assets	12,182	11,808
Accumulated amortization	(5,568)	(5,196)
Intangibles, net	$ 6,614	6,612
Capitalized Patent Costs [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	17 years
Capitalized Patent Costs [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	20 years
Purchased Patents and Intellectual Property [Member]
Intangible assets acquired:
Intangible assets amount	$ 250	250
Purchased Patents and Intellectual Property [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	3 years
Purchased Patents and Intellectual Property [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	10 years
Existing Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	5 years
Intangible assets acquired:
Intangible assets amount	$ 1,560	1,560
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	7 years
Intangible assets acquired:
Intangible assets amount	$ 290	$ 290