Segment Information - Additional Information (Detail) $ in Millions	6 Months Ended
Sep. 30, 2020 USD ($) Location Facility Terminal Plant Sector Segment
Segment Reporting [Abstract]
Number of sectors \| Sector	2
Number of reportable business segments \| Segment	4
Cement plant locations \| Location	8
Slag grinding facility \| Facility	1
Cement distribution terminals \| Terminal	29
Readymix concrete batch plants	20
Aggregates processing plants	3
Gypsum wallboard plants	5
Proportionate consolidation of share of joint venture revenues and operating earnings	50.00%
Accrued capital expenditures \| $	$ 2.9

Future cash outflow to pay for purchases of fixed assets that have occurred.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4332-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4313-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=121583591&loc=d3e4304-108586

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