Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Jul. 27, 2017	Feb. 10, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Operating income (loss)			$ 382,175	$ 354,431	$ 270,700
Purchase price paid for business acquisition			36,761	400,488	32,427
Goodwill			$ 205,211	198,370
Fairborn Acquisition [Member]
Business Acquisition [Line Items]
Business acquisition, date of acquisition			Feb. 10, 2017
Business acquisition purchase price		$ 400,500
Other assets		2,820
Asset retirement obligation		2,820
Provisional other assets recorded previously		4,000
Provisional asset retirement obligation recorded previously		4,000
Depreciation and amortization			$ 14,600	1,900
Operating income (loss)				(2,394)
Material nonrecurring charges					$ 5,500
Property and equipment		314,897
Goodwill		$ 64,485
Fairborn Acquisition [Member] | Fair Value Adjustment To Inventory [Member]
Business Acquisition [Line Items]
Operating income (loss)			$ 500	$ 1,500
Wildcat Minerals LLC [Member]
Business Acquisition [Line Items]
Business acquisition, effective date of acquisition			Jul. 27, 2017
Purchase price paid for business acquisition	$ 36,800
Current assets	3,100
Property and equipment	28,300
Intangible and other assets	1,400
Current liabilities	2,800
Goodwill	$ 6,800