Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025
Debt Instrument [Line Items]
Finance lease obligations (see Note 6)	$ 138,952	$ 158,473
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Other long-term debt	Other long-term debt
Total debt	$ 6,585,115	$ 7,204,275
Unamortized discount, debt issuance costs and fair value adjustments made in purchase accounting	(136,510)	(168,166)
Less: current portion of long-term debt	57,753	503,825
Total long-term debt	6,390,852	6,532,284
2022 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	673,750	680,750
2023 Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	601,283	607,450
Inmarsat Original Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		300,000
Inmarsat Term Loan Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	1,274,000	1,287,000
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	188,730
Former Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt		19,652
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt		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