Operations in Different Geographic Areas (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Jan. 03, 2020	Sep. 27, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 28, 2018	Jun. 29, 2018	Mar. 30, 2018	Jan. 03, 2020		Dec. 28, 2018		Dec. 29, 2017
Operations in Different Geographic Areas [Line Items]
Property, equipment and leasehold improvements, net		$ 61,587				$ 46,103				$ 61,587		$ 46,103
Revenues		110,114	$ 101,548	$ 106,506	$ 99,031	92,143	$ 95,302	$ 95,621	$ 96,457	417,199	[1]	379,523	[1]	$ 347,799	[1]
United States
Operations in Different Geographic Areas [Line Items]
Property, equipment and leasehold improvements, net		60,074				44,181				60,074		44,181
Revenues	[1]									351,856		334,422		308,406
Foreign Countries
Operations in Different Geographic Areas [Line Items]
Property, equipment and leasehold improvements, net		$ 1,513				$ 1,922				1,513		1,922
Revenues	[1]									$ 65,343		$ 45,101		$ 39,393

[1] Geographic revenues are allocated based on the location of the client.