Goodwill and Purchased Intangible Assets - Details of Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2018	Dec. 29, 2017
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, accumulated amortization	$ (34,265)	$ (32,070)
Definite lives intangible assets, net carrying amount	20,405
Intangible Assets, gross carrying value	63,657	63,657
Intangible Assets, net carrying value	29,392	31,587
American Integration Technologies LLC [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	19,000	19,000
Definite lives intangible assets, accumulated amortization	(18,307)	(17,998)
Definite lives intangible assets, net carrying amount	$ 693	1,002
Useful Life (in years)	7 years
American Integration Technologies LLC [Member] | Trade Name [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 1,900	1,900
Definite lives intangible assets, accumulated amortization	$ (1,900)	(1,900)
Useful Life (in years)	6 years
American Integration Technologies LLC [Member] | Intellectual Properties/Know-How [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 1,600	1,600
Definite lives intangible assets, accumulated amortization	(1,371)	(1,257)
Definite lives intangible assets, net carrying amount	$ 229	343
Useful Life (in years)	7 years
Thermal [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 9,900	9,900
Definite lives intangible assets, accumulated amortization	(3,383)	(2,887)
Definite lives intangible assets, net carrying amount	$ 6,517	7,013
Useful Life (in years)	10 years
Thermal [Member] | Trade Name [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 1,170	1,170
Definite lives intangible assets, accumulated amortization	$ (1,170)	(1,170)
Useful Life (in years)	6 years
Thermal [Member] | Intellectual Properties/Know-How [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 12,300	12,300
Definite lives intangible assets, accumulated amortization	(4,712)	(4,023)
Definite lives intangible assets, net carrying amount	$ 7,588	8,277
Thermal [Member] | Intellectual Properties/Know-How [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	8 years
Thermal [Member] | Intellectual Properties/Know-How [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	12 years
FDS [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Definite lives intangible assets, gross carrying amount	$ 8,800	8,800
Definite lives intangible assets, accumulated amortization	(3,422)	(2,835)
Definite lives intangible assets, net carrying amount	$ 5,378	5,965
Useful Life (in years)	7 years 6 months
UCT [Member] | Trade Name [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite lives intangible assets	$ 8,987	$ 8,987