Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Sep. 30, 2023	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Valuation and Qualifying Accounts Disclosure [Line Items]
Charged to costs and expenses		$ 69,000
Deferred Tax Asset Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance			$ 353,642	$ 150,047	$ 78,071
Charged to costs and expenses			76,859	139,687	71,976
Charged to goodwill	[1]			63,908
Ending Balance			$ 430,501	$ 353,642	$ 150,047

[1] Related to the acquisition of Inmarsat