Goodwill and Purchased Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 25, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization of finite-lived intangibles	$ 1,231	$ 1,440
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	7 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