Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016
Senior Notes
Total senior notes long-term, net	$ 575,330	$ 575,304
Other Long-Term Debt
Other	568	562
Total other long-term debt, net	459,007	370,498
Total other long-term debt, net	459,007	370,498
Less: current portion of other long-term debt, net	277	274
Other long-term debt, net	458,730	370,224
Total debt, net	1,034,337	945,802
Less: current portion	277	274
Long-term debt, net	1,034,060	945,528
Revolving Credit Facility [Member]
Other Long-Term Debt
Credit Facility	200,000	180,000
Ex-Im Credit Facility [Member]
Senior Notes
Unamortized premium (discount) and debt issuance costs	(34,338)	(28,221)
Other Long-Term Debt
Credit Facility	264,400
Credit Facility	292,777	218,157
Unamortized premium (discount) and debt issuance costs	(34,338)	(28,221)
2020 Notes [Member]
Senior Notes
Principal amounts of Senior Notes issued	575,000	575,000
Unamortized premium (discount) and debt issuance costs	330	304
Total senior notes, net	575,330	575,304
Total senior notes, net	575,330	575,304
Less: current portion of the senior notes	0	0
Total senior notes long-term, net	575,330	575,304
Other Long-Term Debt
Unamortized premium (discount) and debt issuance costs	$ 330	$ 304