Revenue - Schedule of Revenue by Payer Type and Percentage of Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 03, 2021	Mar. 28, 2020
Disaggregation Of Revenue [Line Items]
Total revenue	$ 417,160	$ 355,223
Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	100.00%	100.00%
Medicaid MCO
Disaggregation Of Revenue [Line Items]
Total revenue	$ 232,884	$ 209,873
Medicaid MCO | Customer Concentration Risk | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	55.80%	59.10%
Medicaid
Disaggregation Of Revenue [Line Items]
Total revenue	$ 103,497	$ 94,960
Medicaid | Customer Concentration Risk | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	24.80%	26.70%
Commercial
Disaggregation Of Revenue [Line Items]
Total revenue	$ 47,003	$ 41,235
Commercial | Customer Concentration Risk | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	11.30%	11.60%
Medicare
Disaggregation Of Revenue [Line Items]
Total revenue	$ 32,016	$ 8,552
Medicare | Customer Concentration Risk | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	7.70%	2.40%
Self-pay
Disaggregation Of Revenue [Line Items]
Total revenue	$ 1,760	$ 603
Self-pay | Customer Concentration Risk | Revenue from Contract with Customer, Product and Service Benchmark
Disaggregation Of Revenue [Line Items]
Percentage of total revenue	0.40%	0.20%