Senior Notes and Other Long-Term Debt - Components of Long-Term Debt (Detail) - USD ($)	Dec. 31, 2016	Mar. 31, 2016
Senior Notes
Total senior notes long-term, net	$ 575,368,000	$ 575,304,000
Other Long-Term Debt
Other	583,000	562,000
Total other long-term debt, net	272,060,000	370,498,000
Total other long-term debt, net	272,060,000	370,498,000
Less: current portion of other long-term debt, net	284,000	274,000
Other long-term debt, net	271,776,000	370,224,000
Total debt, net	847,428,000	945,802,000
Less: current portion	284,000	274,000
Long-term debt, net	847,144,000	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	(32,657,000)	(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	368,000	304,000
Total senior notes, net	575,368,000	575,304,000
Total senior notes, net	575,368,000	575,304,000
Less: current portion of the senior notes	0	0
Total senior notes long-term, net	$ 575,368,000	$ 575,304,000