Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2025	Mar. 31, 2025
Debt Instrument [Line Items]
Finance lease obligations (see Note 1)		$ 142,937	$ 158,473
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]		Other long-term debt	Other long-term debt
Total debt		$ 6,406,911	$ 7,204,275
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting		(126,420)	(168,166)
Less: current portion of long-term debt		36,916	503,825
Total long-term debt		6,243,575	6,532,284
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		675,500	680,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		602,824	607,450
Immarsat Original Term Loan Facility [ Member]
Debt Instrument [Line Items]
Principal amount of debt	[1]		300,000
Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,277,250	1,287,000
Former Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	[2]		19,652
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	[3]		442,550
2027 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		600,000	600,000
2028 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		400,000	400,000
Inmarsat 2029 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		1,975,000	1,975,000
2031 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		$ 733,400	$ 733,400

[1] On November 21, 2025, the remaining borrowings under Inmarsat's original senior secured term loan facility (the Original Inmarsat Term Loan Facility) were repaid early in full.

[2] On October 15, 2025, the Former Ex-Im Credit Facility was fully repaid at maturity.

[3] On May 2, 2025, the 2025 Notes were redeemed in full.