Other Noncurrent Liabilities and Redeemable/Noncontrolling Interests - Additional Information (Detail) $ in Millions	Sep. 30, 2025 USD ($) Facility	Mar. 31, 2025 USD ($)
Minority Interest [Line Items]
Non-controlling interest balances	$ 61
Redeemable non-controlling interest balances	$ 67
Redeemable noncontrolling interest		$ 39
Michigan
Minority Interest [Line Items]
Behavioral health care facilities with outside owners holding non-controlling minority interest | Facility	2
Outside Owners | Acute Care Facility | Texas
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	7.00%
Outside Owners | Acute Care Facility | Nevada
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	5.00%
Outside Owners | Behavioral Health Care Facility | Arizona
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	49.00%
Outside Owners | Behavioral Health Care Facility | Ohio
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	30.00%
Outside Owners | Behavioral Health Care Facility | Washington
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	20.00%
Outside Owners | Behavioral Health Care Facility | Missouri
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	25.00%
Outside Owners | Behavioral Health Care Facility | Iowa
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	48.00%
Outside Owners | Behavioral Health Care Facility One | Michigan
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	25.00%
Outside Owners | Behavioral Health Care Facility Two | Michigan
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	49.00%
Outside Owners | Surgery center | Nevada
Minority Interest [Line Items]
Percentage of non-controlling, minority ownership interests held by outside owners	49.00%
Hospital | Behavioral Health Care Facility | Pennsylvania
Minority Interest [Line Items]
Non-controlling ownership interests by subsidiaries	20.00%