Derivative Transactions - Schedule of Cash Settlements and Net (Gains) and Net Losses on Mark-to-Market Adjustments for Changes in Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Derivatives, Fair Value [Line Items]
Total net unrealized mark-to-market (gains) loss	$ (1,082)	$ 1,788
Total net realized loss (gains)	840	(159)
Diesel Fuel Option Collars [Member]
Derivatives, Fair Value [Line Items]
Total net unrealized mark-to-market (gains) loss	(1,082)	69
Total net realized loss (gains)	$ 840	7
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Total net unrealized mark-to-market (gains) loss		1,726
Total net realized loss (gains)		(166)
Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Total net unrealized mark-to-market (gains) loss		$ (7)