Consolidated Variable Interest Entities - Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 29, 2020	Mar. 31, 2019
Variable Interest Entity [Line Items]
Revenues	$ 617,253	$ 673,484
Cost of revenues	465,208	517,159
Selling, general and administrative expenses	137,326	135,035
Total operating expenses	610,581	660,851
Program profit	6,672	12,633
Other expense, net	785	1,720
Net income (loss)	(4,943)	(5,719)
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Revenues	87,191	63,260
Cost of revenues	68,525	50,402
Selling, general and administrative expenses	18,017	18,289
Total operating expenses	86,542	68,691
Program profit	649	(5,431)
Other expense, net	(1,049)	(354)
Net income (loss)	$ (400)	$ (5,785)