Relationship with Universal Health Realty Income Trust and Other Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Net revenues	$ 4,495,245,000	$ 3,963,027,000	$ 12,878,781,000	$ 11,714,213,000
Acute Care Hospital Services
Related Party Transaction [Line Items]
Net revenues	2,630,065,000	2,253,819,000	$ 7,380,328,000	6,617,586,000
Relationship with Universal Health Realty Income Trust
Related Party Transaction [Line Items]
Percentage of advisory fee on average invested real estate assets			0.70%		0.70%	0.70%	0.70%
Pre-tax share of income from the Trust	260,000	300,000	$ 828,000	914,000
Dividends received from the Trust	583,000	575,000	1,700,000	1,700,000
Carrying value of investment in Trust	4,800,000		4,800,000		$ 5,800,000
Market value of investment in Trust	$ 30,800,000		$ 30,800,000		$ 29,300,000
Relationship with Universal Health Realty Income Trust | Other Related Party Transactions
Related Party Transaction [Line Items]
Trust outstanding shares held, percentage	5.70%		5.70%
Relationship with Universal Health Realty Income Trust | Advisory Fee
Related Party Transaction [Line Items]
Net revenues	$ 1,400,000	$ 1,400,000	$ 4,200,000	$ 4,100,000