Commitments and Contingencies - Additional Information (Detail) £ in Millions				3 Months Ended		9 Months Ended			12 Months Ended
	Oct. 10, 2024 USD ($)	Sep. 27, 2024 USD ($) Plaintiffs	Mar. 28, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2024 GBP (£)	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2024 GBP (£)	Dec. 31, 2023 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Purchased several excess policies through commercial insurance carriers per occurrence excess claim amount				$ 30,000,000		$ 30,000,000
Self-insured for professional and general liability, current				70,000,000		70,000,000								$ 70,000,000
Compensation liability claims				136,000,000		136,000,000								130,000,000
Pre-tax decrease to reserves for self-insured workers' compensation liability claims								$ 10,000,000
Compensation and related benefits				58,000,000		58,000,000								55,000,000
Maximum insurance deductible				5,000,000		5,000,000
Self insurance reserve amount exhausted				10,000,000		10,000,000
Purchased several excess policies through commercial insurance amount exhausted				30,000,000		30,000,000
District Facilities
Commitments and Contingencies Disclosure [Line Items]
Projected aggregate development and construction cost				439,000,000		439,000,000
Development and construction cost incurred				$ 295,000,000		$ 295,000,000
Lease initial terms				75 years		75 years							75 years
Committment to expend						$ 12,000,000
Projected commitment expend period						12 years	12 years
Department of Human Services
Commitments and Contingencies Disclosure [Line Items]
Repayment of legal settlement amount on demand						$ 4,000,000
Amount claimed from over payments of legal settlements									$ 4,000,000	$ 7,000,000	$ 8,000,000	$ 7,000,000
Amount claimed from over payments of legal settlements due to change in calculations										$ 3,000,000	2,000,000	$ 2,000,000
The Pavilion Behavioral Health System
Commitments and Contingencies Disclosure [Line Items]
Aggregate insurance coverage				$ 221,000,000		221,000,000
The Pavilion Behavioral Health System | Compensatory Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 475,000,000		$ 60,000,000
The Pavilion Behavioral Health System | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 120,000,000		$ 475,000,000
Cumberland Hospital for Children and Adolescents
Commitments and Contingencies Disclosure [Line Items]
Number of plaintiffs | Plaintiffs		40
Cumberland Hospital for Children and Adolescents | Compensatory Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded		$ 60,000,000
Cumberland Hospital for Children and Adolescents | Trebled Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded		180,000,000
Cumberland Hospital for Children and Adolescents | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded		$ 120,000,000
Cumberland Hospital for Children and Adolescents | Compensatory Damages, Trebled Damages And Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Number of plaintiffs | Plaintiffs		3
Subsequent Event | The Pavilion Behavioral Health System | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Timeline of remittitur	21 days
Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				250,000,000		250,000,000
Earthquake | California, New Madrid Seismic Zone, Pacific Northwest Seismic Zone, Alaska and certain counties in Nevada
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				50,000,000		50,000,000
Earthquake Wind Hail and Flood
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible				5,000,000		5,000,000
All Other Events
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible				5,000,000		5,000,000
Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Property insurance | £							£ 1,500.0
Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability				10,000,000		10,000,000
Purchased several excess policies through commercial insurance carriers per occurrence				25,000,000		25,000,000
Commercial property insurance policies covering catastrophic losses				$ 1,000,000,000		$ 1,000,000,000
Lease initial terms				10 years		10 years							10 years
Maximum | Cumberland Hospital for Children and Adolescents | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded		$ 1,050,000.00
Maximum | Subsequent Event | The Pavilion Behavioral Health System | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 475,000,000
Maximum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible				5.00%		5.00%							5.00%
Maximum | Earthquake | CALIFORNIA
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				$ 100,000,000		$ 100,000,000
Maximum | Earthquake | Faulty Zones of UNITED STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				100,000,000		100,000,000
Maximum | Earthquake | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				40,000,000		40,000,000
Maximum | Earthquake | OTHER STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				250,000,000		250,000,000
Maximum | Earthquake | California, New Madrid Seismic Zone, Pacific Northwest Seismic Zone, Alaska and certain counties in Nevada
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				100,000,000		100,000,000
Maximum | Flood
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				100,000,000		100,000,000
Maximum | Flood | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				1,000,000		1,000,000
Maximum | Flood | Texas
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses				$ 10,000,000		$ 10,000,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Lease initial terms				5 years		5 years							5 years
Loss on business interruption insurance recovery						$ 15,000,000
Minimum | District Facilities
Commitments and Contingencies Disclosure [Line Items]
Committment to expend						$ 75,000,000
Minimum | Subsequent Event | The Pavilion Behavioral Health System | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 120,000,000
Minimum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible				3.00%		3.00%							3.00%
Professional Liability | The Pavilion Behavioral Health System
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts				$ 10,000,000		$ 10,000,000
Professional Liability | Cumberland Hospital for Children and Adolescents
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts				10,000,000		10,000,000
General Liability | The Pavilion Behavioral Health System
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts				3,000,000		3,000,000
General Liability | Cumberland Hospital for Children and Adolescents
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts				3,000,000		3,000,000
General And Professional Liability Insurance Policies
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability				30,000,000	$ 5,000,000	44,000,000		$ 25,000,000
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability				480,000,000		480,000,000								431,000,000
Subsidiaries | Professional Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £													£ 18.5
Subsidiaries | Professional Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability				20,000,000		20,000,000			20,000,000					20,000,000	$ 20,000,000	$ 10,000,000	$ 5,000,000	$ 5,000,000	$ 5,000,000	$ 10,000,000
Subsidiaries | General Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £													£ 25.0
Subsidiaries | General Liability | Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability				3,000,000		3,000,000			3,000,000					3,000,000	3,000,000	$ 3,000,000	$ 3,000,000	$ 3,000,000	$ 3,000,000	$ 3,000,000
Subsidiaries | General And Professional Liability Insurance Policies | Maximum
Commitments and Contingencies Disclosure [Line Items]
Purchased several excess policies through commercial insurance carriers per occurrence				$ 175,000,000		$ 175,000,000			$ 162,000,000		$ 250,000,000			$ 165,000,000	$ 155,000,000