Commitments and Contingencies - Additional Information (Detail) £ in Millions		3 Months Ended				12 Months Ended
	Mar. 28, 2024 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2024 GBP (£)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2024 GBP (£)	Dec. 31, 2021 USD ($)	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		$ 20,000,000
Self-insured for professional and general liability, current		70,000,000				$ 70,000,000
Compensation liability claims		132,000,000				130,000,000
Pre-tax decrease to reserves for self-insured workers' compensation liability claims					$ 10,000,000
Compensation and related benefits		55,000,000				55,000,000
Maximum insurance deductible		5,000,000
Self insurance reserve amount exhausted		20,000,000
Purchased several excess policies through commercial insurance amount exhausted		20,000,000
District Facilities
Commitments and Contingencies Disclosure [Line Items]
Projected aggregate development and construction cost		439,000,000
Development and construction cost incurred		$ 229,000,000
Lease initial terms		75 years									75 years
Committment to expend		$ 5,000,000
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
The Pavilion Behavioral Health System | Compensatory Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 60,000,000
The Pavilion Behavioral Health System | Punitive Damages
Commitments and Contingencies Disclosure [Line Items]
Damages awarded	$ 475,000,000
Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		250,000,000
Earthquake Wind Hail and Flood
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible		5,000,000
All Other Events
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible		5,000,000
Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Property insurance | £			£ 1,500
Maximum
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		20,000,000
Purchased several excess policies through commercial insurance carriers per occurrence		25,000,000
Commercial property insurance policies covering catastrophic losses		$ 1,000,000,000
Lease initial terms		10 years									10 years
Maximum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible		5.00%									5.00%
Maximum | Earthquake | CALIFORNIA
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		$ 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
Maximum | Earthquake | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		40,000,000
Maximum | Earthquake | OTHER STATES
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		250,000,000
Maximum | Flood
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		100,000,000
Maximum | Flood | PUERTO RICO
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		1,000,000
Maximum | Flood | Texas
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses		$ 10,000,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Lease initial terms		5 years									5 years
Loss on business interruption insurance recovery		$ 25,000,000
Minimum | District Facilities
Commitments and Contingencies Disclosure [Line Items]
Committment to expend		$ 75,000,000
Minimum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible		3.00%									3.00%
Professional Liability | The Pavilion Behavioral Health System
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts		$ 10,000,000
General Liability | The Pavilion Behavioral Health System
Commitments and Contingencies Disclosure [Line Items]
Self-insured retention amounts		3,000,000
General And Professional Liability Insurance Policies
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		7,000,000		$ 5,000,000	$ 20,000,000	25,000,000	16,000,000
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability		447,000,000				431,000,000
Subsidiaries | Professional Liability | Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability | £											£ 16
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	$ 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
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
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				$ 165,000,000	$ 162,000,000		$ 250,000,000			$ 155,000,000