Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($)	Jun. 30, 2019	Mar. 31, 2019
Debt Instrument [Line Items]
Principal amount of debt	$ 1,427,739,000	$ 1,439,560,000
Unamortized discount and debt issuance costs	(25,131,000)	(26,720,000)
Less: current portion of long-term debt	19,652,000	19,937,000
Total long-term debt	1,382,956,000	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	0	0
Ex-Im Credit Facility [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 127,739,000	$ 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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Amount of unamortized debt discount (premium) and debt issuance costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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