Financial Information Related to Operations by Segment (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023 USD ($) kt	Sep. 30, 2022 USD ($) kt	Sep. 30, 2023 USD ($) kt	Sep. 30, 2022 USD ($) kt	Mar. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Revenue	$ 622,236	$ 605,068	$ 1,223,757	$ 1,166,455
Operating Earnings	219,364	201,395	398,518	357,359
Corporate General and Administrative Expense	(16,576)	(13,627)	(28,255)	(25,447)
Other Non-Operating Income	1,605	(664)	1,818	(1,299)
Earnings Before Interest and Income Taxes	204,393	187,104	372,081	330,613
Interest Expense, net	(10,204)	(8,580)	(22,443)	(15,910)
Earnings before Income Taxes	194,189	178,524	349,638	314,703
Capital Expenditures	29,454	28,335	65,453	43,249
Depreciation, Depletion and Amortization			73,879	68,874
Identifiable Assets	2,917,094		2,917,094		$ 2,781,002
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	682,887	667,384	1,346,797	1,283,918
Depreciation, Depletion and Amortization	37,197	34,645	73,879	68,874
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(31,744)	(37,186)	(67,010)	(66,018)
Revenue	31,744	37,186	67,010	66,018
Consolidation, Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(28,907)	(25,130)	(56,030)	(51,445)
Cement [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	$ 360,751	$ 319,460	$ 689,783	$ 603,976
Cement Sales Volume | kt	2,129	2,145	4,142	4,138
Operating Earnings	$ 121,429	$ 98,779	$ 195,490	$ 161,127
Capital Expenditures	14,487	4,893	26,757	13,879
Depreciation, Depletion and Amortization	22,187	$ 20,258	43,866	$ 40,311
Identifiable Assets	$ 2,014,557		$ 2,014,557		1,905,227
Cement [Member] | Operating Segments [Member] | Wholly-Owned [Member]
Segment Reporting Information [Line Items]
Cement Sales Volume | kt	1,959	1,981	3,807	3,786
Operating Earnings	$ 111,083	$ 91,623	$ 181,985	$ 148,873
Cement [Member] | Operating Segments [Member] | Joint Venture [Member]
Segment Reporting Information [Line Items]
Cement Sales Volume | kt	170	164	335	352
Operating Earnings	$ 10,346	$ 7,156	$ 13,505	$ 12,254
Cement [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	9,251	12,361	19,388	18,652
Concrete and Aggregates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	69,887	69,613	140,340	131,231
Operating Earnings	4,640	7,276	11,674	13,008
Capital Expenditures	5,854	13,688	9,074	14,340
Depreciation, Depletion and Amortization	4,962	4,351	9,993	8,552
Identifiable Assets	238,440		238,440		234,767
Concrete and Aggregates [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	3,783	0	6,821	0
Gypsum Wallboard [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	209,233	224,638	428,330	440,965
Operating Earnings	85,705	89,761	176,562	173,829
Capital Expenditures	5,452	8,391	16,480	12,470
Depreciation, Depletion and Amortization	5,548	5,589	11,009	11,152
Identifiable Assets	414,747		414,747		421,425
Recycled Paperboard [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue	43,016	53,673	88,344	107,746
Operating Earnings	7,590	5,579	14,792	9,395
Capital Expenditures	2,597	1,018	5,865	1,855
Depreciation, Depletion and Amortization	3,708	3,742	7,427	7,459
Identifiable Assets	168,659		168,659		163,797
Recycled Paperboard [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	18,710	24,825	40,801	47,366
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Capital Expenditures	1,064	345	7,277	705
Depreciation, Depletion and Amortization	792	$ 705	1,584	$ 1,400
Other, net [Member]
Segment Reporting Information [Line Items]
Identifiable Assets	$ 80,691		$ 80,691		$ 55,786