Goodwill and Purchased Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 24, 2016	Jun. 30, 2017	Jun. 24, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of finite-lived intangibles	$ 1,200	$ 1,400	$ 2,462	$ 2,879
Minimum [Member] | Trade Name [Member] | American Integration Technologies LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			6 years
Minimum [Member] | Trade Name [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			6 years
Minimum [Member] | Customer Relationships [Member] | American Integration Technologies LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			6 years
Minimum [Member] | Customer Relationships [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			7 years
Minimum [Member] | Customer Relationships [Member] | Miconex [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			7 years
Minimum [Member] | Intellectual Properties/Know-How [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			7 years
Minimum [Member] | Intellectual Properties/Know-How [Member] | Miconex [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			7 years
Maximum [Member] | Trade Name [Member] | American Integration Technologies LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			10 years
Maximum [Member] | Trade Name [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			10 years
Maximum [Member] | Customer Relationships [Member] | American Integration Technologies LLC [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			10 years
Maximum [Member] | Customer Relationships [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			12 years
Maximum [Member] | Customer Relationships [Member] | Miconex [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			12 years
Maximum [Member] | Intellectual Properties/Know-How [Member] | Marchi Thermal Systems Inc [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			12 years
Maximum [Member] | Intellectual Properties/Know-How [Member] | Miconex [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated economic lives for intangible assets			12 years