Reportable Segments - Revenue from contracts with customers by geographic location (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	$ 165,480	$ 117,335
INF
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	84,426	77,273
BTS
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	43,112	40,062
GEO
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	37,942	0
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	162,405	114,770
United States | INF
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	84,426	77,273
United States | BTS
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	40,442	37,497
United States | GEO
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	37,537	0
Foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	3,075	2,565
Foreign | INF
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	0	0
Foreign | BTS
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	2,670	2,565
Foreign | GEO
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross revenues	$ 405	$ 0