Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($)	Dec. 31, 2019	Mar. 31, 2019
Debt Instrument [Line Items]
Finance lease obligations (see Note 6)	$ 67,515,000
Total debt	1,595,428,000	$ 1,439,560,000
Unamortized discount and debt issuance costs	(22,636,000)	(26,720,000)
Less: current portion of long-term debt	30,101,000	19,937,000
Total long-term debt	1,542,691,000	1,392,903,000
2027 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	600,000,000	600,000,000
2025 Notes [Member]
Debt Instrument [Line Items]
Principal amount of debt	700,000,000	700,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	110,000,000	0
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 117,913,000	$ 139,560,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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