Schedule of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
Inventory [Line Items]
Inventories	$ 238,869	$ 258,159
Raw Materials and Material-in-Progress [Member]
Inventory [Line Items]
Inventories	105,943	121,628
Finished Cement [Member]
Inventory [Line Items]
Inventories	24,003	24,089
Aggregates [Member]
Inventory [Line Items]
Inventories	7,309	7,787
Gypsum Wallboard [Member]
Inventory [Line Items]
Inventories	7,612	8,477
Paperboard [Member]
Inventory [Line Items]
Inventories	9,793	8,602
Frac Sand [Member]
Inventory [Line Items]
Inventories	2,729	1,696
Repair Parts and Supplies [Member]
Inventory [Line Items]
Inventories	76,048	79,878
Fuel and Coal [Member]
Inventory [Line Items]
Inventories	$ 5,432	$ 6,002