Reportable Segments - Summarized Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019	Dec. 28, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	$ 162,689	$ 127,974	$ 328,169	$ 245,309
Segment income before taxes	6,559	9,140	12,153	16,200
Assets	897,115		897,115		$ 893,137
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
Operating Segments | INF
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	89,366	83,547	174,841	161,319
Segment income before taxes	15,797	14,691	29,137	27,265
Assets	294,115		294,115		303,239
Operating Segments | BTS
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	37,166	45,372	80,690	85,646
Segment income before taxes	5,409	7,499	10,828	13,416
Assets	132,107		132,107		131,967
Operating Segments | GEO
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	38,233	0	76,193	0
Segment income before taxes	6,145	0	13,758	0
Assets	351,334		351,334		365,605
Elimination of inter-segment revenues
Segment Reporting, Revenue Reconciling Item [Line Items]
Gross revenues	(2,076)	(945)	(3,555)	(1,656)
Segment income before taxes	27,351	22,190	53,723	40,681
Assets	119,559		119,559		$ 92,326
Corporate
Segment Reporting, Revenue Reconciling Item [Line Items]
Segment income before taxes	$ (20,792)	$ (13,050)	$ (41,570)	$ (24,481)