Franchise Rights Acquired, Goodwill and Other Intangible Assets - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 30, 2024 USD ($) Segment	Apr. 01, 2023 USD ($)	Dec. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Goodwill And Intangible Assets Disclosure [Line Items]
Number of reportable segment | Segment	1
Number of operating segment | Segment	1
Finite-lived intangible assets, aggregate amortization expense	$ 9,290	$ 8,519
Net book value of goodwill	$ 242,258		$ 243,441	$ 155,998
Franchise right maturity period	7 years
Behavioral Reporting Unit
Goodwill And Intangible Assets Disclosure [Line Items]
Net book value of goodwill	$ 152,516
Clinical Reporting Unit
Goodwill And Intangible Assets Disclosure [Line Items]
Net book value of goodwill	$ 89,742
All Reporting Units
Goodwill And Intangible Assets Disclosure [Line Items]
Percentage of estimated fair value in excess of carrying amount	25.00%
Franchise rights acquired | Maximum
Goodwill And Intangible Assets Disclosure [Line Items]
Finite-lived intangible assets, estimated useful life (in years)	1 year
Franchise rights acquired | United States
Goodwill And Intangible Assets Disclosure [Line Items]
Net book value of franchise rights acquired	$ 122,923
Indefinite-lived intangible assets, impairment charges	$ 251,431
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges
Percentage of franchise rights acquired	97.90%
Franchise rights acquired | United Kingdom
Goodwill And Intangible Assets Disclosure [Line Items]
Net book value of franchise rights acquired	$ 2,628
Indefinite-lived intangible assets, impairment charges	$ 155
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges
Percentage of franchise rights acquired	2.10%
Franchise rights acquired | Australia
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges	$ 4,074
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges
Franchise rights acquired | New Zealand
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges	$ 2,328
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]	Asset Impairment Charges