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Goodwill and Other Intangible Assets - Additional Information (Detail)				3 Months Ended					6 Months Ended	9 Months Ended		12 Months Ended
	Jun. 24, 2025 USD ($)	May 04, 2025 USD ($)	May 05, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2025 USD ($)	Mar. 29, 2025 USD ($)	Sep. 28, 2024 USD ($)	Mar. 30, 2024 USD ($)	Jun. 24, 2025 USD ($)	Sep. 30, 2025 USD ($) Segment	Sep. 28, 2024 USD ($)	Dec. 28, 2024 USD ($) Segment
Goodwill And Intangible Assets Disclosure [Line Items]
Number of reportable segments \| Segment												1
Number of operating segments \| Segment										1		1
Finite-lived intangible assets, aggregate amortization expense				$ 26,319,000	$ 24,696,000		$ 8,124,000		$ 12,405,000		$ 25,886,000
Goodwill impairment		$ 0	$ 0
Franchise right maturity period										7 years
Total other intangible assets				$ 533,947,000	$ 533,947,000					$ 533,947,000		$ 357,998,000
Fresh Start Accounting
Goodwill And Intangible Assets Disclosure [Line Items]
Total other intangible assets	$ 529,000,000								$ 529,000,000
Behavioral Reporting Unit
Goodwill And Intangible Assets Disclosure [Line Items]
Goodwill impairment						$ 0	$ 0
Percentage of goodwill held						62.70%	63.00%				63.00%
Behavioral Reporting Unit \| Minimum
Goodwill And Intangible Assets Disclosure [Line Items]
Percentage of estimated fair value in excess of carrying amount						55.00%	100.00%				100.00%
Clinical Reporting Unit
Goodwill And Intangible Assets Disclosure [Line Items]
Goodwill impairment						$ 0	$ 0
Percentage of goodwill held						37.30%	37.00%				37.00%
Clinical Reporting Unit \| Minimum
Goodwill And Intangible Assets Disclosure [Line Items]
Percentage of estimated fair value in excess of carrying amount						60.00%	20.00%				20.00%
All Reporting Units
Goodwill And Intangible Assets Disclosure [Line Items]
Goodwill impairment								$ 0
All Reporting Units \| Minimum
Goodwill And Intangible Assets Disclosure [Line Items]
Percentage of estimated fair value in excess of carrying amount								25.00%
Database
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated margin rate	19.00%
Discount rate	17.00%
Behavioral developed technology
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated royalty rate	4.00%
Discount rate	17.00%
Clinincal developed technology
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated royalty rate	5.00%
Discount rate	17.00%
Clinical customers/subscribers
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated attrition rate	40.00%
Discount rate	17.00%
Behavioral customers/subscribers
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated attrition rate	25.00%
Discount rate	17.00%
B2B customers/subscribers
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated attrition rate	10.00%
Discount rate	17.00%
Trade names
Goodwill And Intangible Assets Disclosure [Line Items]
Estimated royalty rate	6.00%
Discount rate	17.00%
Franchise rights acquired
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges		$ 0	$ 0
Franchise rights acquired \| United States
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges						$ 27,549,000	$ 54,295,000	$ 251,431,000
Indefinite-lived franchise rights acquired percentage						100.00%
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]						Asset Impairment Charges	Asset Impairment Charges	Asset Impairment Charges
Franchise rights acquired \| United Kingdom
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges							$ 2,750,000	$ 155,000
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]							Asset Impairment Charges	Asset Impairment Charges
Franchise rights acquired \| Australia
Goodwill And Intangible Assets Disclosure [Line Items]
Indefinite-lived intangible assets, impairment charges								$ 4,074,000
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								$ 2,328,000
Impairment, Intangible Asset, Indefinite-Lived (Excluding Goodwill), Statement of Income or Comprehensive Income [Extensible Enumeration]								Asset Impairment Charges