Commitments and Contingencies - Additional Information (Detail) £ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2023 GBP (£)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2023 GBP (£)	Dec. 31, 2022 USD ($)	Jun. 01, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability, current	$ 55,000,000								$ 74,000,000
Compensation liability claims	128,000,000								125,000,000
Compensation and related benefits	55,000,000								55,000,000
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
Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Maximum insurance deductible										$ 2,500,000
Cygnet Health Care Limited
Commitments and Contingencies Disclosure [Line Items]
Property insurance | £		£ 1,500
Maximum | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	$ 1,000,000,000
Percentage of insurance deductible	5.00%							5.00%
Maximum | Earthquake | CALIFORNIA
Commitments and Contingencies Disclosure [Line Items]
Commercial property insurance policies covering catastrophic losses	$ 150,000,000
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 | Wind Storms
Commitments and Contingencies Disclosure [Line Items]
Percentage of insurance deductible	3.00%							3.00%
General And Professional Liability Insurance Policies
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability			$ 16,000,000	$ 52,000,000
General and Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Self-insured for professional and general liability	$ 392,000,000								$ 372,000,000
Subsidiaries | Professional Liability
Commitments and Contingencies Disclosure [Line Items]
Purchased several excess policies through commercial insurance carriers per occurrence											$ 2,500,000
Purchased several excess policies through commercial insurance carriers per occurrence excess claim amount											10,000,000
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										10,000,000	$ 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
Subsidiaries | General And Professional Liability Insurance Policies | Maximum
Commitments and Contingencies Disclosure [Line Items]
Purchased several excess policies through commercial insurance carriers per occurrence	$ 165,000,000		$ 162,000,000	$ 155,000,000										$ 250,000,000