Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 29, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 617,253	$ 673,484
Operating income	7,457	14,353
Amortization of intangible assets	8,047	8,657	$ 8,700
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0
Operating income	(9,513)	(10,653)
Amortization of intangible assets	0	0
GMS \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	457,444	504,480
Operating income	12,603	25,792
Amortization of intangible assets	4,115	4,258
NSS \| Operating Segments
Segment Reporting Information [Line Items]
Revenues	159,809	169,004
Operating income	4,367	(786)
Amortization of intangible assets	$ 3,932	$ 4,399

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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