Discontinued Operations - Net Sales and Losses from Discontinued Operations (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 04, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations		$ (23,979)	$ (6,742)	$ (2,142)
Income tax benefit		5,738	1,336	1,560
Loss from discontinued operations (Note 3)		(18,241)	(5,406)	(582)
Test and Inspection Services
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations (Note 3)	$ (10,034)
Test and Inspection Services | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales		13,590	38,629	45,905
Loss from discontinued operations		(10,807)	(6,742)	(2,142)
Income tax benefit		2,600	1,336	1,560
Loss on the sale of discontinued operations		(13,172)	0	0
Income tax benefit on the sale of discontinued operations		3,138	0	0
Loss from discontinued operations (Note 3)		$ (18,241)	$ (5,406)	$ (582)