Reportable Segments - Revenue by Customer Type (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	$ 162,689	$ 127,974	$ 328,169	$ 245,309
INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	87,889	82,790	172,315	160,062
BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	36,641	45,184	79,752	85,247
GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	38,159	0	76,102	0
Public and quasi-public sector
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	111,905	89,819	221,635	173,113
Public and quasi-public sector | INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	67,723	72,415	133,107	140,540
Public and quasi-public sector | BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	17,658	17,404	35,492	32,573
Public and quasi-public sector | GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	26,524	0	53,036	0
Private sector
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	50,784	38,155	106,534	72,196
Private sector | INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	20,166	10,375	39,208	19,522
Private sector | BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	18,983	27,780	44,260	52,674
Private sector | GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	$ 11,635	$ 0	$ 23,066	$ 0