Segment Breakdown of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Segment Reporting Information [Line Items]
Goodwill	$ 132,515	$ 132,515
Operating Segments [Member] \| Cement [Member]
Segment Reporting Information [Line Items]
Goodwill	8,359	8,359
Operating Segments [Member] \| Gypsum Wallboard [Member]
Segment Reporting Information [Line Items]
Goodwill	116,618	116,618
Operating Segments [Member] \| Paperboard [Member]
Segment Reporting Information [Line Items]
Goodwill	$ 7,538	$ 7,538

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details