Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($)	Mar. 31, 2017	Mar. 31, 2016
Senior Notes
Total senior notes long-term, net	$ 575,380,000	$ 575,304,000
Other Long-Term Debt
Other	288,000	562,000
Total other long-term debt, net	273,391,000	370,498,000
Total other long-term debt, net	273,391,000	370,498,000
Less: current portion of other long-term debt, net	288,000	274,000
Other long-term debt, net	273,103,000	370,224,000
Total debt	848,771,000	945,802,000
Less: current portion	288,000	274,000
Long-term debt, net	848,483,000	945,528,000
Revolving Credit Facility [Member]
Other Long-Term Debt
Credit Facility	0	180,000,000
Ex-Im Credit Facility [Member]
Other Long-Term Debt
Credit Facility	274,600,000
Credit Facility	304,134,000	218,157,000
Unamortized discount and debt issuance costs on the Ex-Im Credit Facility	(31,031,000)	(28,221,000)
2020 Notes [Member]
Senior Notes
Principal amounts of Senior Notes issued	575,000,000	575,000,000
Unamortized premium and debt issuance costs on the 2020 Notes, net	380,000	304,000
Total senior notes, net	575,380,000	575,304,000
Total senior notes, net	575,380,000	575,304,000
Less: current portion of the senior notes	0	0
Total senior notes long-term, net	$ 575,380,000	$ 575,304,000