Eagle Materials (EXP) 10-K 22 May 15 2015 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Mar. 31, 2015	18-May-15	Sep. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Trading Symbol	EXP
Entity Registrant Name	EAGLE MATERIALS INC
Entity Central Index Key	918646
Current Fiscal Year End Date	-28
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		50,232,767
Entity Public Float			$5

Consolidated_Statements_of_Ear

Consolidated Statements of Earnings (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]
Revenues	$1,066,368	$898,396	$642,562
Cost of Goods Sold	812,235	712,937	539,317
Gross Profit	254,133	185,459	103,245
Equity in Earnings of Unconsolidated Joint Venture	44,967	37,811	32,507
Corporate General and Administrative Expense	-30,751	-24,552	-23,918
Other Operating Income (Loss)	3,201	1,368	-1,232
Acquisition and Litigation Expense	-6,880		-10,683
Interest Expense, Net	-11,743	-18,282	-15,823
Earnings before Income Taxes	252,927	181,804	84,096
Income Taxes	-66,074	-57,561	-26,352
Net Earnings	$186,853	$124,243	$57,744
EARNINGS PER SHARE
Basic	$3.77	$2.53	$1.24
Diluted	$3.71	$2.49	$1.22
AVERAGE SHARES OUTSTANDING
Basic	49,604,249	49,090,750	46,622,646
Diluted	50,372,243	49,939,165	47,340,450
CASH DIVIDENDS PER SHARE	$0.40	$0.40	$0.40

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Earnings (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net Earnings	$186,853	$124,243	$57,744
Net Actuarial (Gains) Losses of Defined Benefit Plans:
Unrealized (gain) loss during the period, net of tax (expense) benefit of ($3,746), $1,173 and $1,071	6,173	-2,399	-1,988
Amortization of Net Actuarial Loss, net of tax benefit of $242, $333 and $249	411	840	462
Comprehensive Earnings	$193,437	$122,684	$56,218

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Earnings (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Unrealized (gain) loss during the period, tax (expense) benefit	($3,746)	$1,173	$1,071
Amortization of Net Actuarial Loss, tax benefit	$242	$333	$249

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Current Assets -
Cash and Cash Equivalents	$7,514	$6,482
Accounts and Notes Receivable, net	113,577	102,917
Inventories	235,464	187,096
Prepaid and Other Assets	10,080	10,465
Total Current Assets	366,635	306,960
Property, Plant and Equipment -	1,962,215	1,660,975
Less: Accumulated Depreciation	-740,396	-676,924
Property, Plant and Equipment, net	1,221,819	984,051
Notes Receivable	2,847	3,063
Investment in Joint Venture	47,614	43,008
Goodwill and Intangible Assets, net	211,167	160,690
Other Assets	32,509	13,757
Total Assets	1,882,591	1,511,529
Current Liabilities -
Accounts Payable	77,749	57,098
Accrued Liabilities	46,830	41,520
Income Tax Payable	2,952	702
Current Portion of Long-term Debt	57,045	9,500
Total Current Liabilities	184,576	108,820
Long-term Debt	455,714	371,759
Other Long-term Liabilities	69,055	53,678
Deferred Income Taxes	162,653	145,773
Total Liabilities	871,998	680,030
Stockholders’ Equity –
Preferred Stock, Par Value $0.01; Authorized 5,000,000 Shares; None Issued
Common Stock, Par Value $0.01; Authorized 100,000,000 Shares; Issued and Outstanding 50,245,364 and 50,053,078 Shares, respectively.	502	501
Capital in Excess of Par Value	272,441	253,524
Accumulated Other Comprehensive Losses	-12,067	-5,483
Retained Earnings	749,717	582,957
Total Stockholders’ Equity	1,010,593	831,499
Liabilities and Stockholders' Equity, Total	$1,882,591	$1,511,529

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Mar. 31, 2014
Statement Of Financial Position [Abstract]
Preferred Stock, Par Value	$0.01	$0.01
Preferred Stock, Authorized	5,000,000	5,000,000
Preferred Stock, Issued	0	0
Common Stock, Par Value	$0.01	$0.01
Common Stock, Authorized	100,000,000	100,000,000
Common Stock, Issued	50,245,364	50,053,078
Common Stock, Outstanding	50,245,364	50,053,078

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES
Net Earnings	$186,853	$124,243	$57,744
Adjustments to Reconcile Net Earnings to Net Cash Provided by Operating Activities, Net of Effect of Non-Cash Activity -
Depreciation, Depletion and Amortization	76,299	70,021	56,850
Deferred Income Tax Provision	5,805	5,746	6,155
Stock Compensation Expense	13,030	10,136	9,002
Excess Tax Benefits from Share Based Payment Arrangements	-5,743	-8,067	-6,493
Equity in Earnings of Unconsolidated Joint Venture	-44,967	-37,811	-32,507
Distributions from Joint Venture	40,375	37,750	28,500
Changes in Operating Assets and Liabilities:
Accounts and Notes Receivable	4,196	-12,876	-7,771
Inventories	-38,741	-32,714	-14,186
Accounts Payable and Accrued Liabilities	-11,499	6,504	24,610
Other Assets	520	-3,511	-2,679
Income Taxes Payable	7,993	11,212	5,182
Net Cash Provided by Operating Activities	234,121	170,633	124,407
CASH FLOWS FROM INVESTING ACTIVITIES
Additions to Property, Plant and Equipment	-111,573	-59,490	-53,011
CRS Acquisition	-237,171		-453,420
Net Cash Used in Investing Activities	-348,744	-59,490	-506,431
CASH FLOWS FROM FINANCING ACTIVITIES
Increase (Decrease) in Credit Facility	141,000	-108,000	227,000
Repayment of Senior Notes	-9,500		-4,677
Dividends Paid to Stockholders	-20,072	-19,899	-18,533
Net Proceeds from Offering of Common Stock			154,832
Proceeds from Stock Option Exercises	4,311	14,187	19,645
Shares Redeemed to Settle Employee Taxes on Stock Compensation	-4,166	-2,913	-3,569
Payment of Debt Issuance Costs	-1,661		-1,751
Excess Tax Benefits from Share Based Payment Arrangements	5,743	8,067	6,493
Net Cash Provided by (Used in) Financing Activities	115,655	-108,558	379,440
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,032	2,585	-2,584
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	6,482	3,897	6,481
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$7,514	$6,482	$3,897

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock [Member]	Capital in Excess of Par Value [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Losses [Member]
In Thousands
Beginning balance at Mar. 31, 2012	$472,511	$453	$37,692	$439,882	($5,516)
Net Earnings	57,744			57,744
Net proceeds from Equity Offering	154,832	35	154,797
Stock Option Exercises and Restricted Share Vesting	19,645	8	19,637
Tax Benefit-Stock Option Exercise	6,493		6,493
Dividends to Stockholders	-18,962			-18,962
Stock Compensation Expense	9,002		9,002
Shares Redeemed to Settle Employee Taxes	-3,569	-1	-3,568
Unfunded Pension Liability, net of tax	-1,526				-1,526
Ending Balance at Mar. 31, 2013	696,170	495	224,053	478,664	-7,042
Net Earnings	124,243			124,243
Stock Option Exercises and Restricted Share Vesting	14,187	5	14,182
Tax Benefit-Stock Option Exercise	8,067		8,067
Dividends to Stockholders	-19,950			-19,950
Stock Compensation Expense	10,136	1	10,135
Shares Redeemed to Settle Employee Taxes	-2,913		-2,913
Unfunded Pension Liability, net of tax	1,559				1,559
Ending Balance at Mar. 31, 2014	831,499	501	253,524	582,957	-5,483
Net Earnings	186,853			186,853
Stock Option Exercises and Restricted Share Vesting	4,311	1	4,310
Tax Benefit-Stock Option Exercise	5,743		5,743
Dividends to Stockholders	-20,093			-20,093
Stock Compensation Expense	13,030		13,030
Shares Redeemed to Settle Employee Taxes	-4,166		-4,166
Unfunded Pension Liability, net of tax	-6,584				-6,584
Ending Balance at Mar. 31, 2015	$1,010,593	$502	$272,441	$749,717	($12,067)

Significant_Accounting_Policie

Significant Accounting Policies	12 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	(A) Significant Accounting Policies
	Basis of Presentation –
	The consolidated financial statements include the accounts of Eagle Materials Inc. and its majority-owned subsidiaries (“EXP” or the “Company”), which may be referred to as “our”, “we”, or “us”. All intercompany balances and transactions have been eliminated. EXP is a holding company whose assets consist of its investments in its subsidiaries, joint venture, intercompany balances and holdings of cash and cash equivalents. The businesses of the consolidated group are conducted through EXP’s subsidiaries. The Company conducts one of its cement plant operations through a joint venture, Texas Lehigh Cement Company L.P., which is located in Buda, Texas (the “Joint Venture”). Investments in the Joint Venture and affiliated companies owned 50% or less are accounted for using the equity method of accounting. The Equity in Earnings of Unconsolidated Joint Venture has been included for the same period as our March 31 year end.
	The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Reclassifications – Certain reclassifications have been made to the prior year to conform to the current year presentation.
	Cash and Cash Equivalents –
	Cash equivalents include short-term, highly liquid investments with original maturities of three months or less and are recorded at cost, which approximates market value.
	Accounts and Notes Receivable –
	Accounts and notes receivable have been shown net of the allowance for doubtful accounts of $7.1 million and $5.8 million at March 31, 2015 and 2014, respectively. We perform ongoing credit evaluations of our customers’ financial condition and generally require no collateral from our customers. The allowance for non-collection of receivables is based upon analysis of economic trends in the construction and oil and gas industries, detailed analysis of the expected collectability of accounts receivable that are past due and the expected collectability of overall receivables. We have no significant credit risk concentration among our diversified customer base.
	We had notes receivable totaling approximately $3.3 million at March 31, 2015, of which approximately $0.5 million has been classified as current and presented with accounts receivable on the balance sheet. We lend funds to certain companies in the ordinary course of business, and the notes bear interest, on average, at 3.9%, which will vary based on changes to LIBOR. Remaining unpaid amounts, plus accrued interest, mature on various dates between 2015 and 2017. The notes are collateralized by certain assets of the borrowers, namely property and equipment. We monitor the credit risk of each borrower by focusing on the timeliness of payments, review of credit history and credit metrics and interaction with the borrowers. At March 31, 2015 and 2014, approximately $0.3 million of our allowance for doubtful accounts is related to our notes receivable.
	Inventories –
	Inventories are stated at the lower of average cost (including applicable material, labor, depreciation, and plant overhead) or market. Inventories consist of the following:
		March 31,
		2015			2014
		(dollars in thousands)
	Raw Materials and Materials-in-Progress	$	115,345		$	82,319
	Finished Cement		20,508			19,173
	Gypsum Wallboard		7,741			7,144
	Paperboard		8,493			4,102
	Frac Sand		4,928			275
	Aggregates		11,131			11,815
	Repair Parts and Supplies		62,121			56,119
	Fuel and Coal		5,197			6,149
		$	235,464		$	187,096
	Property, Plant and Equipment –
	Property, plant and equipment are stated at cost. Major renewals and improvements are capitalized and depreciated. Annual maintenance is expensed as incurred. Depreciation is provided on a straight-line basis over the estimated useful lives of depreciable assets and totaled $69.7 million, $67.3 million and $55.1 million for the years ended March 31, 2015, 2014 and 2013, respectively. Raw material deposits are depleted as such deposits are extracted for production utilizing the units-of-production method. Costs and accumulated depreciation applicable to assets retired or sold are eliminated from the accounts and any resulting gains or losses are recognized at such time. The estimated lives of the related assets are as follows:
	Plants		20 to 30 years
	Buildings		20 to 40 years
	Machinery and Equipment		3 to 25 years
	We periodically evaluate whether current events or circumstances indicate that the carrying value of our depreciable assets may not be recoverable. At March 31, 2015 and 2014, management believes no events or circumstances indicate that the carrying value may not be recoverable.
	We idled our gypsum manufacturing facility in Bernalillo, N.M. in December 2009, due to cyclical low gypsum wallboard demand. The carrying value of the Bernalillo plant and equipment at March 31, 2015 was $2.7 million and $0.4 million, respectively, and we continue to depreciate the assets over their estimated useful life. We currently have a strong market position in New Mexico, and our Albuquerque gypsum wallboard facility is operating at close to capacity. We plan on resuming manufacturing at the Bernalillo facility in the future when additional capacity is needed to meet demand for our products. Costs of maintaining the facility during the idling are not significant, and the facility was generating positive cash flow prior to being idled; therefore, we have determined that the value of the plant and equipment is not impaired. We are not currently considering the permanent closure of the Bernalillo facility. Any decision to permanently close Bernalillo would be the result of future changes in the building materials industry in the southwest United States and Rocky Mountain region, including changes in the production capacity or operations of our competitors, demand for gypsum wallboard or general macro-economic conditions, which we do not foresee at the present time. If we were to permanently close the Bernalillo facility, or if our expectations as to its use changed such that we project the future undiscounted cash flows from its operations would be insufficient to recover its carrying value due to the factors described above, or for any other reason, we would recognize impairment at that time.
	Impairment or Disposal of Long-Lived and Intangible Assets –
	We evaluate the recoverability of our long-lived assets and certain identifiable intangibles, such as permits and customer contracts, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets, such as plants, buildings and machinery and equipment, including mining assets, is measured by comparing the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. Such evaluations for impairment are significantly impacted by estimates of future prices for our products, capital needs, economic trends in the construction sector and other factors. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds their fair value. Assets to be disposed of by sale are reflected at the lower of their carrying amount or fair value less cost to sell.
	Goodwill and Intangible Assets –
	Goodwill: Goodwill is subject to at least an annual assessment for impairment by applying a fair-value-based test. We have elected to test for goodwill impairment in the fourth quarter of each fiscal year. The goodwill impairment test is a two-step process, which requires us to make judgments in determining what assumptions to use in the calculation. The first step of the process consists of estimating the fair value of each reporting unit based on a discounted cash flow model using revenues and profit forecasts and comparing those estimated fair values with the carrying value; a second step is performed, if necessary, to compute the amount of the impairment by determining an “implied fair value” of goodwill. Similar to the review for impairment of other long-lived assets, evaluations for impairment are significantly impacted by estimates of future prices for our products, capital needs, economic trends and other factors.
	Intangible Assets: Intangible assets at March 31, 2015 and 2014 consist of the following:
		March 31, 2015
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		5-15 years		$	62,060		$	(5,994	)	$	56,066
	Sales contracts		4 years			2,500			(1,458	)		1,042
	Permits		40 years			27,440			(5,896	)		21,544
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	224,515		$	(13,348	)	$	211,167
		March 31, 2014
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		15 years		$	6,060		$	(1,580	)	$	4,480
	Sales contracts		4 years			2,500			(833	)		1,667
	Permits		40 years			27,240			(5,212	)		22,028
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	168,315		$	(7,625	)	$	160,690
	Amortization expense of intangibles was $5.7 million, $1.7 million and $1.0 million for the years ended March 31, 2015, 2014 and 2013, respectively. Amortization expense is expected to be approximately $13.4 million per year for fiscal year 2016, $13.2 million for fiscal year 2017, $12.7 million for fiscal year 2018, $12.6 million for fiscal year 2019 and $6.2 million for fiscal year 2020.
	Other Assets –
	Other assets are primarily composed of loan fees and financing costs, deferred expenses, and deposits.
	Income Taxes –
	Income taxes are accounted for using the asset and liability method. Deferred taxes are recognized for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities. The effect on deferred taxes of a change in tax rates is recognized in earnings in the period that includes the enactment date. In addition, we recognize future tax benefits to the extent that such benefits are more likely than not to be realized.
	Stock Repurchases –
	Our Board of Directors has approved the repurchase of a cumulative total of 31,610,605 shares, of which approximately 717,300 shares remain available for repurchase at March 31, 2015. We did not repurchase any shares in the open market during the years ended March 31, 2015, 2014 and 2013.
	Revenue Recognition –
Revenue from the sale of cement, gypsum wallboard, paperboard, frac sand, concrete and aggregates is recognized when title and ownership are transferred upon shipment to the customer. Fees for shipping and handling are recorded as revenue, while costs incurred for shipping and handling are recorded as expenses.
We classify amounts billed to customers for freight as revenues and freight costs as cost of goods sold, respectively, in the Consolidated Statements of Earnings. Approximately $124.0 million, $113.1 million and $83.2 million were classified as cost of goods sold in the years ended March 31, 2015, 2014 and 2013, respectively.
Other income (loss) includes lease and rental income, asset sale income, non-inventoried aggregates sales income, distribution center income and trucking income as well as other miscellaneous revenue items and costs which have not been allocated to a business segment.
Comprehensive Income/Losses –
As of March 31, 2015, we have an accumulated other comprehensive loss of $12.1 million, which is net of income taxes of $7.1 million, in connection with recognizing the difference between the fair value of the pension assets and the projected benefit obligation.
Consolidated Cash Flows – Supplemental Disclosures –
Interest payments made during the years ended March 31, 2015, 2014 and 2013 were $15.1 million, $17.0 million and $14.6 million, respectively.
We made net payments of $78.3 million, $41.7 million and $14.8 million for federal and state income taxes in the years ended March 31, 2015, 2014 and 2013, respectively.
Statements of Consolidated Earnings – Supplemental Disclosures –
Maintenance and repair expenses are included in each segment’s costs and expenses. We incurred $86.7 million, $77.4 million and $61.3 million in the years ended March 31, 2015, 2014 and 2013, respectively, which is included in Cost of Goods Sold on the Consolidated Statement of Earnings.
Selling, general and administrative expenses of the operating units are included in Cost of Goods Sold on the Consolidated Statements of Earnings. Corporate general and administrative (“G&A”) expenses include administration, financial, legal, employee benefits and other corporate activities and are shown separately in the consolidated statements of earnings. Corporate G&A also includes stock compensation expense. See Note (J), Stock Option Plans, for more information.
Total selling, general and administrative expenses for each of the periods are summarized as follows:
	For the Years Ended March 31,
	2015			2014			2013
	(dollars in thousands)
Operating Units Selling, G&A	$	49,326		$	50,175		$	39,133
Corporate G&A		30,751			24,552			23,918
	$	80,077		$	74,727		$	63,051
Earnings Per Share –
	For the Years Ended March 31,
	2015			2014			2013
Weighted-Average Shares of Common Stock Outstanding					49,090,750			46,622,646
		49,604,249
Effect of Dilutive Shares:
Assumed Exercise of Outstanding Dilutive Options		1,350,556			1,574,491			1,984,563
Less Shares Repurchased from Proceeds of Assumed Exercised Options		(868,636	)		(1,032,359	)		(1,568,604	)
Restricted Stock Units		286,074			306,283			301,845
Weighted-Average Common Stock and Dilutive Securities Outstanding		50,372,243			49,939,165			47,340,450
The “Less Shares Repurchased from Proceeds of Assumed Exercised Options” line includes unearned compensation related to outstanding stock options.
There were 285,267, 146,696 and 1,082,380 stock options at an average exercise price of $82.72 per share, $65.12 per share and $39.65 per share that were excluded from the computation of diluted earnings per share for the years ended March 31, 2015, 2014 and 2013, respectively, because such inclusion would have been anti-dilutive.
Fair Value Measures –
Certain assets and liabilities are required to be recorded or disclosed at fair value. The estimated fair values of those assets and liabilities have been determined using market information and valuation methodologies. Changes in assumptions or estimation methods could affect the fair value estimates; however, we do not believe any such changes would have a material impact on our financial condition, results of operations or cash flows. There are three levels of inputs that may be used to measure fair value:
Level 1 – Quoted prices for identical assets and liabilities in active markets;
Level 2 – Quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data; and
Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
New Accounting Standards –
In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers.” ASU 2014-09 supersedes the revenue recognition requirements in “Revenue Recognition (Topic 605),” and requires entities to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The standard will be effective for us in the first quarter of fiscal 2018, with early adoption not permitted. There are two transition methods available under the new standard, either cumulative effect or retrospective. We are currently evaluating the impact of this ASU and have not yet selected a transition method.
In April 2015, The Financial Accounting Standards Board issued ASU 2015-03, “Interest-Imputation of Interest (Subtopic 830-30). This standard requires that discounts, premiums or debt issue costs related to borrowings be reported in the balance sheet as a direct reduction of the associated borrowing. The standard will be effective for us in the first quarter of fiscal 2017, and earlier application is permitted for financial statements that have not been previously issued.  The impact of adopting this ASU is not expected to be material.
Acquisition and Litigation Expense
Acquisition and litigation expense consists primarily of expenses incurred during our acquisition, as discussed in Note (B), CRS Acquisition, and significant legal expenses incurred during litigation primarily involving the lawsuit against the Internal Revenue Service (“IRS”). See Note (H), Income Taxes, for more information about the outstanding lawsuit with the IRS.

CRS_Acquisition

CRS Acquisition	12 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
CRS ACQUISITION	(B) CRS ACQUISITION
	On November 14, 2014, Northern White Sand LLC (“NWS”), a wholly owned subsidiary of the Company, completed the acquisition (the “CRS Acquisition”) of the outstanding equity interest in CRS Holdco LLC, CRS Proppants LLC and Great Northern Sand LLC and related entities (collectively “CRS Proppants”). CRS Proppants is a supplier of frac sand to the energy industry, and its business currently consists of a frac sand mine in New Auburn, Wisconsin, and a transload network into Texas and southwest Oklahoma.
	Purchase Price: The purchase price (the “Purchase Price”) of the CRS Acquisition was approximately $237.2 million, including approximately $8.9 million of in-process capital expenditures paid as of the closing date. The purchase price is subject to further adjustment to reflect actual working capital acquired at the closing. We funded the payment of the Purchase Price at closing and expenses incurred in connection with the CRS Acquisition through borrowings under our bank credit facility, which was amended and restated on October 30, 2014. See Footnote (E) of the Notes to Consolidated Financial Statements for more information about the amended bank credit facility.
	Recording of assets acquired and liabilities assumed: The transaction has been accounted for using the acquisition method of accounting which requires, among other things, that assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. The Company has engaged a third-party to perform appraisal valuation to support the Company’s preliminary estimate of the fair value of certain assets acquired in the CRS Acquisition. The working capital amounts paid at the closing are subject to certain changes to reflect actual working capital. Additionally, the amounts assigned to property, plant and equipment and intangible assets, are preliminary and subject to change, though it is possible other values may change as well. Included in the assets acquired, and liabilities assumed, are two long-term sales agreements that included prepayments for future sales under the agreement, with such prepayments classified as liabilities. Additionally, one of the agreements is with a customer that is currently in bankruptcy, and is not expected to fulfill its obligation under the contract. We have been indemnified by the former owner against any loss related to this contract, and such indemnity has been valued at fair value and recorded as an asset at the date of the acquisition.
	The preparation of the valuation of the assets acquired and liabilities assumed in the CRS Acquisition requires the use of significant assumptions and estimates. Critical estimates include, but are not limited to, future expected cash flows, including projected revenues and expenses, and applicable discount rates. These estimates are based on assumptions that we believe to be reasonable. However, actual results may differ from these estimates.
	The following table summarizes the provisional allocation of the estimated Purchase Price to assets acquired and liabilities assumed as of the acquisition date:
	Purchase price allocation at acquisition date (in thousands)	As of
		November 14, 2014
	Cash and cash equivalents	$	219
	Accounts Receivable		14,640
	Inventories		9,627
	Prepaid and Other Assets		753
	Property and Equipment		192,738
	Intangible Assets		56,200
	Indemnity under Sales Agreement		14,810
	Other Assets		1,120
	Accounts Payable		(4,343	)
	Accrued Liabilities		(2,585	)
	Obligations under Long-term Sales Agreements		(28,131	)
	Asset Retirement Obligation		(4,112	)
	Deferred Taxes		(13,765	)
	Total Net Assets		237,171
	Goodwill		—
	Total Estimated Purchase Price	$	237,171
	Intangible Assets: The following table is a summary of the fair value estimates of the identifiable intangible assets (in thousands) and their weighted-average useful lives:
		Weighted			Estimated
		Average Life			Fair Value
	Customer Relationships		4			56,000
	Permits		40			200
	Total Intangible Assets				$	56,200
	Actual and pro forma impact of the CRS Acquisition: The following table presents the net sales and operating loss of CRS Proppants that has been included in our consolidated statement of earnings from November 14, 2014 through the end of the fiscal year:
		Fiscal Year Ended
		March 31, 2015
		(dollars in thousands)
	Revenues	$	28,035
	Operating Loss	$	5,002
	Operating loss shown above has been impacted by approximately $6.4 million of depreciation and amortization and approximately $1.5 million related to the impact of recording acquired inventory at fair value.
	The Company previously reported the estimated purchase price allocation in its Quarterly Report on Form 10-Q for the period ended December 31, 2014.  During the fiscal fourth quarter, we finalized our valuation of the customer relationships, property plant and equipment and both our reclamation liability and reclamation asset.  Also, the changes above, as well as the determination of the tax basis in the entities acquired, impacted our deferred tax liability at the acquisition date.  The impact of the above changes increased our customer relationship intangible asset by approximately $8.0 million, reduced our deferred tax liability by approximately $6.2 million, increased our asset retirement obligation by approximately $3.6 million and decreased property, plant and equipment by approximately $10.9 million.  We made other minor changes to working capital and reclassified certain amounts to reflect post-closing information. The final purchase price allocation is still pending certain working capital and tax basis adjustments.  We will finalize the amounts recognized as the information necessary to complete the analyses is obtained. We expect to finalize these amounts during the first half of fiscal 2016.
	The unaudited pro forma results presented below include the effects of the CRS Acquisition as if it had been consummated as of April 1, 2013. The pro forma results include the amortization associated with an estimate for acquired intangible assets and interest expense associated with debt used to fund the CRS Acquisition and depreciation from the fair value adjustments for property and equipment. To better reflect the combined operating results, material nonrecurring charges directly related to the CRS Acquisition of $1.1 million have been excluded from pro forma net income for fiscal 2015.
		For the Fiscal Year Ended
		March 31,
		2015			2014
		(dollars in thousands)
	Revenues	$	1,124,755		$	961,006
	Net Income	$	188,715		$	107,764
	Earnings per share – basis	$	3.8		$	2.2
	Earnings per share - diluted	$	3.75		$	2.16
	The pro forma results do not include any anticipated synergies or other expected benefits of the CRS Acquisition. Accordingly, the unaudited pro forma results are not necessarily indicative of either future results of operations or results that might have been achieved had the CRS Acquisition been consummated as of April 1, 2013.
	On March 3, 2015, we entered into an asset purchase agreement to acquire a 600,000 ton per year Granulated Ground Blast Furnace Slag (“GGBFS”) plant in South Chicago (the “Skyway Plant”) with Holcim (US) Inc. (“Holcim”) and an affiliate of Holcim (the “Skyway Acquisition”).  Among other applications, GGBFS is used in conjunction with Portland cement to make durable concrete structures.  The Skyway Plant purchases its primary raw material, slag, pursuant to a long term supply agreement with a third party.
	The purchase price (the “Skyway Purchase Price”) to be paid by us in the Skyway Acquisition is approximately $30.0 million in cash, subject to customary post-closing adjustments. We expect to fund the payment of the Skyway Purchase Price and expenses incurred in connection with the Skyway Acquisition through operating cash flow.  We will assume certain liabilities, including contractual obligations, related to the Skyway Plant.  The Skyway Acquisition is conditioned on the closing of the Lafarge S.A.-Holcim Ltd. merger and is expected to close during our fiscal 2016 second quarter.

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Mar. 31, 2015
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	(C) Property, Plant and Equipment
	Cost by major category and accumulated depreciation are summarized as follows:
		March 31,
		2015			2014
		(dollars in thousands)
	Land and Quarries	$	345,991		$	171,987
	Plants		1,378,497			1,357,594
	Buildings, Machinery and Equipment		151,627			111,263
	Construction in Progress		86,100			20,131
			1,962,215			1,660,975
	Accumulated Depreciation		(740,396	)		(676,924	)
		$	1,221,819		$	984,051

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Mar. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses	(D) Accrued Expenses
	Accrued expenses at March 31, 2015 and 2014 consist of the following:
		March 31,
		2015		2014
		(dollars in thousands)
	Payroll and Incentive Compensation	$	19,082	$	12,855
	Benefits		9,951		10,158
	Interest		4,524		4,813
	Property Taxes		3,189		2,801
	Power and Fuel		1,619		2,132
	Legal		1,673		1,831
	Sales and Use Tax		523		658
	Acquisition Related Expenses		1,355		—
	Other		4,914		6,272
		$	46,830	$	41,520

Indebtedness

Indebtedness	12 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Indebtedness	(E) Indebtedness
	Long-term debt consists of the following:
		As of
		March 31,			March 31,
		2015			2014
		(dollars in thousands)
	Bank Credit Facility	$	330,000		$	189,000
	Senior Notes		182,759			192,259
	Total Debt		512,759			381,259
	Less: Current Portion of Long-term Debt		(57,045	)		(9,500	)
	Long-term Debt	$	455,714		$	371,759
	The weighted-average interest rate of Senior Notes was 5.81% for each of the fiscal 2015, 2014 and 2013. The average interest rate of the Senior Notes was 5.80% and 5.81% at March 31, 2015 and 2014, respectively.
	The weighted-average interest rate of bank debt borrowings during fiscal 2015, 2014 and 2013 was 1.5%, 1.9% and 2.0%, respectively. The interest rate on the bank debt was 1.6% and 1.5% at March 31, 2015 and 2014, respectively.
	Our maturities of long-term debt during the next five fiscal years and thereafter are as follows:
	Fiscal Year	Amount
	2016	$	57,045
	2017		8,000
	2018		81,214
	2019		—
	2020		366,500
	Thereafter		—
	Total	$	512,759
	Senior Notes -
	We entered into a Note Purchase Agreement on November 15, 2005 (the “2005 Note Purchase Agreement”) related to our sale of $200.0 million of senior, unsecured notes, designated as Series 2005A Senior Notes (the “Series 2005A Senior Notes”) in a private placement transaction. The Series 2005A Senior Notes, which are guaranteed by substantially all of our subsidiaries, were sold at par and issued in three tranches on November 15, 2005. Since entering into the 2005 Note Purchase Agreement, we have repurchased $81.1 million in principal of the Series 2005A Senior Notes (in periods prior to the fiscal year ended March 31, 2013). Following these repurchases, the amounts outstanding for each of the remaining tranches are as follows:
		Principal			Maturity Date			Interest Rate
	Tranche B	$	57.0 million			15-Nov-15			5.38	%
	Tranche C	$	57.2 million			15-Nov-17			5.48	%
	Interest for each tranche of Notes is payable semi-annually on May 15 and November 15 of each year until all principal is paid for the respective tranche.
	We also entered into an additional Note Purchase Agreement on October 2, 2007 (the “2007 Note Purchase Agreement”) related to our sale of $200.0 million of senior, unsecured notes, designated as Series 2007A Senior Notes (the “Series 2007A Senior Notes”) in a private placement transaction. The Series 2007A Senior Notes, which are guaranteed by substantially all of our subsidiaries, were sold at par and issued in four tranches on October 2, 2007. Since entering into the 2007 Note Purchase Agreement, we have repurchased $122.0 million in principal of the Series 2007A Senior Notes (in periods prior to the fiscal year ended March 31, 2013). During October 2014, Tranche A of the Series 2007A Senior Notes matured and we retired the remaining $9.5 million in notes from this Tranche. Following these repurchases and maturation, the amounts outstanding for each of the four tranches are as follows:
		Principal			Maturity Date			Interest Rate
	Tranche B	$	8.0 million			2-Oct-16			6.27	%
	Tranche C	$	24.0 million			2-Oct-17			6.36	%
	Tranche D	$	36.5 million			2-Oct-19			6.48	%
	Interest for each tranche of Notes is payable semi-annually on April 2 and October 2 of each year until all principal is paid for the respective tranche.
	Our obligations under the 2005 Note Purchase Agreement and the 2007 Note Purchase Agreement (collectively referred to as the “Note Purchase Agreements”) and the Series 2005A Senior Notes and the Series 2007A Senior Notes (collectively referred to as “the Senior Notes”) are equal in right of payment with all other senior, unsecured debt of the Company, including our debt under the Credit Facility. The Note Purchase Agreements contain customary restrictive covenants, including covenants that place limits on our ability to encumber our assets, to incur additional debt, to sell assets, or to merge or consolidate with third parties, as well as certain cross covenants with the Credit Facility. We were in compliance with all financial ratios and tests at March 31, 2015 and throughout the fiscal year.
	Pursuant to a Subsidiary Guaranty Agreement, substantially all of our subsidiaries have guaranteed the punctual payment of all principal, interest, and Make-Whole Amounts (as defined in the Note Purchase Agreements) on the Senior Notes and the other payment and performance obligations of the Company contained in the Senior Notes and in the Note Purchase Agreements. We are permitted, at our option and without penalty, to prepay from time to time at least 10% of the original aggregate principal amount of the Senior Notes at 100% of the principal amount to be prepaid, together with interest accrued on such amount to be prepaid to the date of payment, plus a Make-Whole Amount. The Make-Whole Amount is computed by discounting the remaining scheduled payments of interest and principal of the Senior Notes being prepaid at a discount rate equal to the sum of 50 basis points and the yield to maturity of U.S. treasury securities having a maturity equal to the remaining average life of the Senior Notes being prepaid.
	Bank Debt -
	Our unsecured Credit Facility was amended and restated on October 30, 2014 (the “Amended Credit Facility”). The Amended Credit Facility increased available borrowings from $400.0 million to $500.0 million and extended the term from December 15, 2015 to October 30, 2019. Borrowings under the Amended Credit Facility are guaranteed by substantially all of the Company’s subsidiaries. At the option of the Company, outstanding principal amounts on the Amended Credit Facility bear interest at a variable rate equal to (i) LIBOR, plus an agreed margin (ranging from 100 to 225 basis points), which is to be established quarterly based upon the Company’s ratio of consolidated EBITDA, defined as earnings before interest, taxes, depreciation and amortization, to the Company’s consolidated indebtedness (the “Leverage Ratio”), or (ii) an alternative base rate which is the higher of (a) the prime rate or (b) the federal funds rate plus 1/2% per annum plus an agreed margin (ranging from 0 to 125 basis points). Interest payments are payable, in the case of loans bearing interest at a rate based on the federal funds rate, quarterly, or in the case of loans bearing interest at a rate based on LIBOR, at the end of the LIBOR advance periods, which can be a period of up to nine months at the option of the Company. The Company is also required to pay a commitment fee on unused available borrowings under the Amended Credit Facility ranging from 10 to 35 basis points depending upon the Leverage Ratio. The Amended Credit Facility contains customary covenants that restrict our ability to incur additional debt, encumber our assets, sell assets, make or enter into certain investments, loans or guaranties and enter into sale and leaseback arrangements. The Amended Credit Facility also requires us to maintain a consolidated indebtedness ratio (calculated as consolidated indebtedness to consolidated earnings before interest, taxes, depreciation, amortization, certain transaction-related deductions and other non-cash deductions) of 3.5:1.0 or less and an interest coverage ratio (consolidated earnings before interest, taxes, depreciation, amortization, certain transaction-related deductions and other non-cash deductions to consolidated interest expense) of at least 2.5:1.0. We had $330.0 million of borrowings outstanding at March 31, 2015. Based on our Leverage Ratio, we had $160.8 million of available borrowings, net of the outstanding letters of credit, at March 31, 2015.
	The Credit Facility has a $50.0 million letter of credit facility. Under the letter of credit facility, the Company pays a fee at a per annum rate equal to the applicable margin for Eurodollar loans in effect from time to time plus a one-time letter of credit fee in an amount equal to 0.125% of the initial stated amount. At March 31, 2015, we had $9.2 million of letters of credit outstanding.
	We are leasing one of our cement plants from the city of Sugar Creek, Missouri. The city of Sugar Creek issued industrial revenue bonds to partly finance improvements to the cement plant. The lease payments due to the city of Sugar Creek under the cement plant lease, which was entered into upon the sale of the industrial revenue bonds, are equal in amount to the payments required to be made by the city of Sugar Creek to the holders of the industrial revenue bonds. Because we are the holder of all of the outstanding industrial revenue bonds, no debt is reflected on our financial statements in connection with our lease of the cement plant. At the conclusion of the lease in fiscal 2021, we have the option to purchase the cement plant for a nominal amount.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	12 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	(F) Fair Value of Financial Instruments
	The fair value of our senior notes has been estimated based upon our current incremental borrowing rates for similar types of borrowing arrangements. The fair value of our Senior Notes at March 31, 2015 is as follows:
		Fair Value
		(dollars in thousands)
	Series 2005A Tranche B	$	58,206
	Series 2005A Tranche C		60,911
	Series 2007A Tranche B		8,434
	Series 2007A Tranche C		25,952
	Series 2007A Tranche D		40,777
	The estimated fair value of our long-term debt was based on quoted prices of similar debt instruments with similar terms that are publicly traded (level 2 input). The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable and accrued liabilities approximate their fair values at March 31, 2015 due to the short-term maturities of these assets and liabilities. The fair value of our Credit Facility also approximates its carrying value at March 31, 2015.

Business_Segments

Business Segments	12 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Business Segments	(G) Business Segments
	Operating segments are defined as components of an enterprise that engage in business activities that earn revenues, incur expenses and prepare separate financial information that is evaluated regularly by our chief operating decision maker in order to allocate resources and assess performance. During the quarter ended June 30, 2014, we changed our segment presentation to reflect Oil and Gas Proppants, which had been included in Concrete and Aggregates, as a reportable segment.  We have adjusted the prior segment presentation to reflect this change for comparative purposes.
	We operate in five business segments: Cement, Gypsum Wallboard, Recycled Paperboard, Oil and Gas Proppants and Concrete and Aggregates. These operations are conducted in the U.S. and include the mining of limestone and the manufacture, production, distribution and sale of portland cement (a basic construction material which is the essential binding ingredient in concrete), the mining of gypsum and the manufacture and sale of gypsum wallboard, the manufacture and sale of recycled paperboard to the gypsum wallboard industry and other paperboard converters, the sale of readymix concrete and the mining and sale of aggregates (crushed stone, sand and gravel) and sand used in hydraulic fracturing (“frac sand”). The products that we manufacture, distribute and sell are basic materials with broad application as construction products, building materials, and basic materials used for oil and natural gas extraction.  Our construction productions are used in residential, industrial, commercial and infrastructure construction and include cement, concrete and aggregates.  Our building materials are sold into similar markets and include gypsum wallboard.  Our basic materials used for oil and natural gas extraction include frac sand and oil well cement.
	We operate six cement plants, sixteen cement distribution terminals, five gypsum wallboard plants, including the plant idled in Bernalillo, N.M., a gypsum wallboard distribution center, a recycled paperboard mill, seventeen readymix concrete batch plant locations, four aggregates processing plant locations, two frac sand processing facilities, three frac sand drying facilities and four frac sand trans-load locations. In addition to the four trans-load locations in operation at March 31, 1015, we opened a trans-load location during the first quarter of fiscal 2016 in Kenedy, Texas, and we expect to open a second trans-load location in Fowlerton, Texas during the second quarter of fiscal 2016. The principal markets for our cement products are Texas, northern Illinois (including Chicago), the central plains, the Rocky Mountains, northern Nevada, and northern California. Gypsum wallboard and recycled paperboard are distributed throughout the continental U.S, with the exception of the northeast. Concrete and aggregates are sold to local readymix producers and paving contractors in the Austin, Texas area, north of Sacramento, California and the greater Kansas City, Missouri area, while frac sand is currently sold into shale deposits across the United States.
	We conduct one of our six cement plant operations, Texas Lehigh Cement Company LP in Buda, Texas, through a Joint Venture. For segment reporting purposes only, we proportionately consolidate our 50% share of the Joint Venture’s revenues and operating earnings, which is consistent with the way management reports the segments within the Company for making operating decisions and assessing performance.
	We account for intersegment sales at market prices. The following table sets forth certain financial information relating to our operations by segment:
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Revenues -
	Cement		$	488,644		$	438,224		$	304,125
	Gypsum Wallboard			437,514			387,016			306,529
	Paperboard			142,690			130,178			121,930
	Oil and Gas Proppants			81,381			19,557			—
	Concrete and Aggregates			107,892			96,908			56,287
				1,258,121			1,071,883			788,871
	Less: Intersegment Revenues			(65,533	)		(62,094	)		(49,987	)
	Less: Joint Venture Revenues			(126,220	)		(111,393	)		(96,322	)
			$	1,066,368		$	898,396		$	642,562
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Intersegment Revenues -
	Cement		$	9,598		$	8,952		$	2,850
	Paperboard			55,060			52,119			46,393
	Concrete and Aggregates			875			1,023			744
			$	65,533		$	62,094		$	49,987
	Cement Sales Volumes (M tons) -
	Wholly-Owned			3,744			3,580			2,390
	Joint Venture			1,055			1,013			913
				4,799			4,593			3,303
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Operating Earnings -
	Cement	$		117,527		$	89,486		$	46,228
	Gypsum Wallboard			145,871			114,852			69,712
	Paperboard			31,512			23,610			25,200
	Oil and Gas Proppants			(2,546	)		(4,890	)		(1,253	)
	Concrete and Aggregates			6,736			212			(5,388	)
	Other, net			3,201			1,368			21
	Sub-Total			302,301			224,638			134,520
	Corporate General and Administrative			(30,751	)		(24,552	)		(23,918	)
	Acquisition, Litigation and Other Expense			(6,880	)		—			(10,683	)
	Earnings Before Interest and Income Taxes			264,670			200,086			99,919
	Interest Expense, net			(11,743	)		(18,282	)		(15,823	)
	Earnings Before Income Taxes		$	252,927		$	181,804		$	84,096
	Cement Operating Earnings -
	Wholly-Owned		$	72,560		$	51,675		$	13,721
	Joint Ventures			44,967			37,811			32,507
			$	117,527		$	89,486		$	46,228
	Capital Expenditures -
	Cement		$	27,086		$	12,226		$	15,583
	Gypsum Wallboard			7,129			4,825			2,682
	Paperboard			1,888			3,354			804
	Oil and Gas Proppants			61,484			34,264			—
	Concrete and Aggregates			13,851			4,572			33,932
	Other, net			135			249			10
			$	111,573		$	59,490		$	53,011
	Depreciation , Depletion and Amortization -
	Cement		$	31,839		$	31,829		$	20,658
	Gypsum Wallboard			20,092			20,981			21,045
	Paperboard			8,251			8,716			8,824
	Oil and Gas Proppants			8,839			1,707			—
Concrete and Aggregates			5,533			5,205			5,212
Corporate and Other			1,745			1,583			1,111
		$	76,299		$	70,021		$	56,850
		As of March 31,
		2015			2014			2013
		(dollars in thousands)
Identifiable Assets
Cement		$	777,956		$	762,578		$	756,158
Gypsum Wallboard			403,279			412,566			425,866
Paperboard			123,519			125,045			129,226
Oil and Gas Proppants			455,572			92,199			48,929
Concrete and Aggregates			96,610			87,364			87,054
Other, net			25,655			31,777			29,000
		$	1,882,591		$	1,511,529		$	1,476,233
Segment operating earnings, including the proportionately consolidated 50% interest in the revenues and expenses of the Joint Venture, represent revenues less direct operating expenses, segment depreciation, and segment selling, general and administrative expenses. We account for intersegment sales at market prices. Corporate assets consist primarily of cash and cash equivalents, general office assets and miscellaneous other assets.
The basis used to disclose Identifiable Assets, Capital Expenditures and Depreciation, Depletion conforms with the equity method, and is similar to how we disclose these accounts in our Consolidated Balance Sheets and Consolidated Statements of Earnings.
The segment breakdown of goodwill at March 31, 2015 and 2014 is as follows:
		For the Years Ended March 31,
		2015			2014
		(dollars in thousands)
Cement		$	8,359		$	8,359
Gypsum Wallboard			116,618			116,618
Paperboard			7,538			7,538
		$	132,515		$	132,515

Income_Taxes

Income Taxes	12 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	(H) Income Taxes
	The provision for income taxes includes the following components:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Current Provision (Benefit) -
	Federal	$	62,424		$	49,604		$	19,108
	State		(2,155	)		2,211			1,089
			60,269			51,815			20,197
	Deferred Provision (Benefit) -
	Federal		(962	)		7,691			5,173
	State		6,767			(1,945	)		982
			5,805			5,746			6,155
	Provision for Income Taxes	$	66,074		$	57,561		$	26,352
	The effective tax rates vary from the federal statutory rates due to the following items:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Earnings Before Income Taxes	$	252,927		$	181,804		$	84,096
	Income Taxes at Statutory Rate	$	88,524		$	63,631		$	29,434
	Increases (Decreases) in Tax Resulting from -
	State Income Taxes, net		4,582			173			1,346
	Statutory Depletion in Excess of Cost		(4,367	)		(3,512	)		(3,110	)
	Domestic Production Activities Deduction		(6,853	)		(3,453	)		(1,895	)
	Meals and Entertainment Disallowance		647			503			337
	Penalties on Uncertain Tax Positions		—			213			215
	IRS Settlement		(16,559	)		—			—
	Other		100			6			25
	Provision for Income Taxes	$	66,074		$	57,561		$	26,352
	Effective Tax Rate		26%			32	%		31	%
	The deferred income tax provision results from the following temporary differences in the recognition of revenues and expenses for tax and financial reporting purposes:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Excess Tax Depreciation and Amortization	$	2,259		$	6,875		$	7,038
	Bad Debts		(142	)		(224	)		(73	)
	Uniform Capitalization		1,296			(1,127	)		(14	)
	Accrual Changes		(611	)		(1,075	)		(1,169	)
	Uncertain Tax Position Accruals		—			213			173
	Prepaid Insurance		(331	)		424			—
	State Income Taxes, net		6,060			(1,319	)		1,130
	Long-term Incentive Compensation Plans		(1,792	)		(373	)		1,293
	Other		(934	)		1,033			(1,093	)
		$	5,805		$	5,746		$	6,155
	Components of deferred income taxes are as follows:
		March 31,
		2015			2014
		(dollars in thousands)
	Items Giving Rise to Deferred Tax Liabilities -
	Excess Tax Depreciation and Amortization	$	(153,045	)	$	(144,519	)
	Depletion		(18,374	)		(100	)
	Repair Parts		(3,376	)		(4,545	)
	State Income Taxes, net		(13,708	)		(7,648	)
	Other		(5,359	)		(9,125	)
	Total Deferred Tax Liabilities	$	(193,862	)	$	(165,937	)
	Items Giving Rise to Deferred Tax Assets -
	Accrual Changes	$	10,557		$	9,946
	Bad Debts		2,264			2,122
	Uniform Capitalization		835			2,131
	Deferred Revenue		4,382			—
	Long-term Incentive Compensation Plan		8,318			6,526
	Other		7,118			—
	Total Deferred Tax Assets	$	33,474		$	20,725
	Deferred income taxes are classified in the consolidated balance sheet as follows:
	March 31,
	2015			2014
	(dollars in thousands)
Prepaid and Other Assets	$	2,265		$	561
Deferred Income Taxes	$	(162,653	)	$	(145,773	)
Uncertain tax position –
We are subject to audit examinations at federal, state and local levels by tax authorities in those jurisdictions who may challenge the treatment or reporting of any return item. The tax matters challenged by the tax authorities are typically complex; therefore, the ultimate outcome of these challenges is subject to uncertainty.
Reconciliation of the consolidated liability for gross unrecognized tax benefits, excluding interest, from April 1, 2012 to March 31, 2015, is as follows:
	For the Years Ended March 31,
	2015			2014			2013
	(dollars in thousands)
Balance at Beginning of Year	$	24,802		$	24,589		$	25,890
Increase related to prior tax positions		—			213			215
Decrease related to prior tax positions		(24,802	)		—			(1,516	)
Payments		—			—			—
	$	—		$	24,802		$	24,589
We recognize penalties associated with uncertain tax positions as part of the tax provision, while interest associated with uncertain tax positions is included in interest expense. The following is a summary of the amounts of interest and penalties recognized in relation to our uncertain tax position:
	For the Years Ended March 31,
	2015			2014			2013
	(dollars in thousands)
Accrued interest recognized	$	(3,847	)	$	641		$	409
Accrued penalties recognized	$	(6,475	)	$	213		$	173
There was no accrued interest or penalties related to our uncertain tax position during the fiscal year ended March 31, 2015.  Accrued interest and penalties related to our uncertain tax positions totaled $4.4 million and $3.2 million, respectively, at March 31, 2014.
In May 2011, we filed a lawsuit against the Internal Revenue Service (“IRS”) in Federal District Court to recover all of the amounts paid to the IRS with respect to our uncertain tax position for 2001 to 2006. In September 2014 we reached a tentative agreement with the IRS to settle this case, and that agreement was approved by the U.S. Department of Justice in January 2015.  Under the terms of the settlement agreement, we dismissed our lawsuit seeking to recover taxes, interest and penalties paid, in exchange for the IRS conceding 40% of the penalties, plus related interest, to date.  The impact from the settlement agreement was approximately $17 million, including state benefits, which was recorded as a reduction of income tax expense during the fourth quarter of fiscal 2015.  The related interest refund of approximately $4.4 million was also recorded during the fourth quarter of fiscal 2015.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Mar. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	(I) Commitments and Contingencies
	Our operations and properties are subject to extensive and changing federal, state and local laws, regulations and ordinances governing the protection of the environment, as well as laws relating to worker health and workplace safety. We carefully consider the requirements mandated by such laws and regulations and have procedures in place at all of our operating units to monitor compliance. Any matters which are identified as potential exposures under these laws and regulations are carefully reviewed by management to determine our potential liability. Although management is not aware of any exposures which require an accrual under generally accepted accounting principles, there can be no assurance that prior or future operations will not ultimately result in violations, claims or other liabilities associated with these regulations.
	We have certain deductible limits under our workers’ compensation and liability insurance policies for which reserves are established based on the undiscounted estimated costs of known and anticipated claims. We have entered into standby letter of credit agreements relating to workers’ compensation and auto and general liability self-insurance. At March 31, 2015, we had contingent liabilities under these outstanding letters of credit of approximately $9.2 million.
	We are currently contingently liable for performance under $14.8 million in performance bonds required by certain states and municipalities, and their related agencies. The bonds are principally for certain reclamation obligations and mining permits. We have indemnified the underwriting insurance company against any exposure under the performance bonds. In our past experience, no material claims have been made against these financial instruments.
	EPA Notice of Violation
	On October 5, 2010, Region IX of the EPA issued a Notice of Violation and Finding of Violation (“NOV”) alleging violations by our subsidiary, Nevada Cement Company (“NCC”), of the Clean Air Act (“CAA”). The NOV alleges that NCC made certain physical changes to its facility in the 1990s without first obtaining permits required by the Prevention of Significant Deterioration requirements and Title V permit requirements of the CAA. The EPA also alleges that NCC has failed to submit to the EPA since 2002 certain reports required by the National Emissions Standard for Hazardous Air Pollutants General Provisions and the Portland Cement Manufacturing Industry Standards. On March 12, 2014, the EPA Region IX issued a second NOV to NCC. The second NOV is materially similar to the 2010 NOV except that it alleges violations of the new source performance standards (“NSPS”) for Portland cement plants. The NOVs state that the EPA may seek penalties although it does not propose or assess any specific level of penalties or specify what relief the EPA will seek for the alleged violations. NCC believes it has meritorious defenses to the allegations in the NOVs. NCC met with the EPA in December 2010, September 2012 and May 2014 to present its defenses and to discuss a resolution of the alleged violations. The EPA and NCC remain in discussions regarding the alleged violations. If a negotiated settlement cannot be reached, NCC intends to vigorously defend these matters in any enforcement action that may be pursued by the EPA. As a part of a settlement, or should NCC fail in its defense in any enforcement action, NCC could be required to make substantial capital expenditures to modify its facility and incur increased operating costs. NCC could also be required to pay significant civil penalties. Additionally, an enforcement action could take many years to resolve the underlying issues alleged in the NOV. We are currently unable to determine the final outcome of this matter or the impact of an unfavorable determination upon our financial position or results of operations.
	Domestic Wallboard Antitrust Litigation
	Since late December 2012, several purported class action lawsuits were filed in various United States District Courts, including the Eastern District of Pennsylvania, Western District of North Carolina and the Northern District of Illinois, against the Company’s subsidiary, American Gypsum Company LLC (“American Gypsum”), alleging that American Gypsum conspired with other wallboard manufacturers to fix the price for drywall sold in the United States in violation of federal antitrust laws and, in some cases related provisions of state law. The complaints allege that the defendant wallboard manufacturers conspired to increase prices through the announcement and implementation of coordinated price increases, output restrictions, and other restraints of trade, including the elimination of individual “job quote” pricing. In addition to American Gypsum, the defendants in these lawsuits include CertainTeed Corp., USG Corporation and United States Gypsum (together “USG”), New NGC, Inc., Lafarge North America, Temple Inland Inc. (“TIN”) and PABCO Building Products LLC. On April 8, 2013, the Judicial Panel on Multidistrict Litigation (“JPML”) transferred and consolidated all related cases to the Eastern District of Pennsylvania for coordinated pretrial proceedings.
	On June 24, 2013, the direct and indirect purchaser plaintiffs filed consolidated amended class action complaints. The direct purchasers’ complaint added the Company as a defendant. The plaintiffs in the consolidated class action lawsuits bring claims on behalf of purported classes of direct or indirect purchasers of wallboard from January 1, 2012 to the present for unspecified monetary damages (including treble damages) and in some cases injunctive relief. On July 29, 2013, the Company and American Gypsum answered the complaints, denying all allegations that they conspired to increase the price of drywall and asserting affirmative defenses to the plaintiffs’ claims.
	On March 17, 2015, a group of homebuilders filed a complaint against the defendants, including American Gypsum, based upon the same conduct alleged in the consolidated class action complaints.  On March 24, 2015, the JPML transferred this action to the multidistrict litigation already pending in the Eastern District of Pennsylvania.
	In 2014, USG and TIN entered into agreements with counsel representing the direct and indirect purchaser classes pursuant to which they agreed to settle all claims against them.  On March 16, 2015, the court entered orders preliminarily approving USG and TIN’s settlements with the direct and indirect purchaser plaintiffs.  Initial discovery in this litigation is complete.  At this stage we are unable to estimate the amount of any reasonably possible loss or range of reasonably possible losses. American Gypsum denies the allegations in these lawsuits and will vigorously defend itself against these claims. Defendants’ motions for summary judgement were filed in the first quarter of fiscal 2016.
	Other
	In the ordinary course of business, we execute contracts involving indemnifications that are standard in the industry and indemnifications specific to a transaction such as the sale of a business. These indemnifications might include claims relating to any of the following: environmental and tax matters; intellectual property rights; governmental regulations and employment-related matters; customer, supplier, construction contractor and other commercial contractual relationships; and financial matters. While the maximum amount to which we may be exposed under such agreements cannot be estimated, it is the opinion of management that these indemnifications are not expected to have a material adverse effect on the Company’s consolidated financial position, results of operations or cash flows. We currently have no outstanding guarantees of third party debt.
	Our paperboard operation, Republic Paperboard Company LLC (“Republic”), is a party to a long-term variable-priced paper supply agreement with St. Gobain pursuant to which Republic is obligated to sell to St. Gobain at least 90% of the gypsum-grade recycled paperboard requirements for three of St. Gobain’s wallboard plants. This comprises approximately 15% to 20% of Republic’s current annual output of gypsum-grade recycled paperboard.
	We have certain forward purchase contracts, primarily for natural gas, that expire during calendar 2015. The contracts are for approximately 25% of our anticipated natural gas usage.
	We have certain operating leases covering manufacturing, transportation and certain other facilities and equipment. Rental expense for fiscal years 2015, 2014 and 2013 totaled $5.9 million, $3.2 million and $1.6 million, respectively. Minimum annual rental commitments as of March 31, 2015, under noncancellable leases are set forth as follows (dollars in thousands):
	Fiscal Year	Amount
	2016	$	11,043
	2017	$	9,834
	2018	$	7,610
	2019	$	6,544
	2020	$	4,171
	Thereafter	$	13,758

Stock_Option_Plans

Stock Option Plans	12 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Plans	(J) Stock Option Plans
	On August 7, 2013 our stockholders approved the Eagle Materials Inc. Amended and Restated Incentive Plan (the “Plan”), which increased the shares we are authorized to issue as awards by 3,000,000 (1,500,000 of which may be stock awards). Under the terms of the Plan, we can issue equity awards, including stock options, restricted stock units (“RSUs”), restricted stock and stock appreciation rights to employees of the Company and members of the Board of Directors. Awards that were already outstanding prior to the approval of the Plan on August 7, 2013 remain outstanding. The Compensation Committee of our Board of Directors specifies the terms for grants of equity awards under the Plan.
	Long-Term Compensation Plans –
	Options. In June 2014, the Compensation Committee of the Board of Directors approved an incentive equity award of an aggregate of 193,636 stock options pursuant to the Plan to certain officers and key employees (the “Fiscal 2015 Employee Stock Option Grant”) that will be earned if our ten year return on equity is at least 15% at March 31, 2015.  If this criterion is not met, all of the stock options will be forfeited.  If the criterion is met, the award may be reduced by the Compensation Committee based on individual performance goals.  The performance criterion was met at March 31, 2015; therefore, all stock options were earned. The stock options will vest ratably over a three year period. The first third of the stock options vested on the determination date, with the remaining stock options vesting on March 31, 2016 and 2017.  The stock options have a term of ten years from the date of grant. In August 2014, we granted 18,515 stock options to members of the Board of Directors (the “Fiscal 2015 Board of Directors Grant”). Stock options granted under the Fiscal 2015 Board of Directors Grant vest immediately and can be exercised from the date of grant until their expiration on the tenth anniversary of the date of grant. The Fiscal 2015 Employee Stock Option Grant and Fiscal 2015 Board of Directors Grant were valued at the grant date using the Black-Scholes option pricing model.
	All stock options issued during fiscal 2015 and 2014 were valued at the grant date using the Black-Scholes option pricing model. The weighted-average assumptions used in the Black-Scholes model to value the option awards in fiscal 2015 and 2014 are as follows:
		2015			2014
	Dividend Yield		2	%		2	%
	Expected Volatility		44.8	%		44.6	%
	Risk Free Interest Rate		1.86	%		2.04	%
	Expected Life		6.0 years			7.0 years
	Stock option expense for all outstanding stock option awards was approximately $6.2 million, $5.3 million and $4.0 million, for the years ended March 31, 2015, 2014 and 2013, respectively. At March 31, 2015, there was approximately $11.4 million of unrecognized compensation cost related to outstanding stock options which is expected to be recognized over a weighted-average period of 3.3 years.
	The following table represents stock option activity for the years presented:
		For the Years Ended March 31,
		2015						2014					2013
		Number			Weighted			Number			Weighted		Number			Weighted
		of			Average			of			Average		of			Average
		Shares			Exercise			Shares			Exercise		Shares			Exercise
					Price						Price					Price
	Outstanding Options at Beginning of Year		2,788,999		$	41.83			3,022,592		$	37.83		3,241,322		$	36.11
	Granted		297,151		$	86.41			256,989		$	68		569,679		$	34.64
	Exercised		(151,085	)	$	32.38			(485,582	)	$	29.72		(746,131	)	$	27.64
	Cancelled		(1,269,500	)	$	47.43			(5,000	)	$	53.22		(42,278	)	$	42.21
	Outstanding Options at End of Year		1,665,565		$	46.37			2,788,999		$	41.83		3,022,592		$	37.83
	Options Exercisable at End of Year		1,035,166						818,215					986,187
	Weighted Average Fair Value of Options Granted during the Year				$	32.31					$	26.35				$	13.28
	The following table summarizes information about stock options outstanding at March 31, 2015:
		Options Outstanding									Options Exercisable
	Range of Exercise Prices	Number of			Weighted			Weighted			Number of		Weighted
		Shares			Average			Average			Shares		Average
		Outstanding			Remaining			Exercise			Outstanding		Exercise
					Contractual			Price					Price
					Life
	$23.17 - $30.74		592,210			4.19		$	26.5			589,210	$	26.48
	$33.08 - $40.78		487,968			6.91		$	33.95			308,352	$	34
	$53.22 - $74.10		283,236			7.82		$	66.58			118,089	$	66.59
	$79.90 - $93.56		302,151			9.31		$	86.42			19,515	$	91.71
			1,665,565			6.54		$	46.37			1,035,166	$	34.52
	At March 31, 2015, the aggregate intrinsic value for outstanding and exercisable options was approximately $61.9 million and $50.8 million, respectively. The total intrinsic value of options exercised during the fiscal year ended March 31, 2015 was approximately $9.6 million.
	Restricted Stock Units. Expense related to RSUs was approximately $1.6 million in the fiscal year ended March 31, 2013. There was no expense related to RSUs for the fiscal years ended March 31, 2015 and 2014. At March 31, 2015, there were approximately 20,000 unvested RSUs, with approximately $0.1 million of unearned compensation, net of estimated forfeitures, which will be recognized over a weighted-average period of 1.0 year.
	Restricted Stock. In June 2014, the Compensation Committee approved the granting of an aggregate of 80,416 shares of restricted stock to certain officers and key employees (the “Fiscal 2015 Employee Restricted Stock Award”) that will be earned if our ten year return on equity is at least 15% at March 31, 2015. If this criterion is not met, all of the shares will be forfeited. If the criterion is met, the award may be reduced by the Compensation Committee based on individual performance goals. The performance criterion was met at March 31, 2015; therefore, all shares were earned. Restriction on the shares will lapse ratably over five years. The first fifth lapsed on May 8, 2015, and the remaining restrictions lapsing on March 31, 2016 through 2019. The value of the Fiscal 2015 Employee Restricted Stock Award, net of estimated forfeitures, is being expensed over a five year period. In August 2014, we granted 7,457 shares of restricted stock to members of the Board of Directors (the “Board of Directors Fiscal 2014 Restricted Stock Award”). Awards issued under the Board of Directors Fiscal 2015 Restricted Stock Award do not fully vest until the retirement of each director, in accordance with the Company’s director retirement policy.
	Expense related to restricted shares was $6.7 million, $4.8 million and $3.4 million in fiscal years ended March 31, 2015, 2014 and 2013, respectively. At March 31, 2015, there were approximately 500,000 shares with remaining restrictions for which $17.0 million of unearned compensation, net of estimated forfeitures, will be recognized over a weighted-average period of 2.5 years.
	The number of shares available for future grants of stock options, restricted stock units, stock appreciation rights and restricted stock under the Plan was 4,907,503 at March 31, 2015. Of the available shares, up to 1,491,297 can be used for future restricted stock and restricted stock unit grants.

Net_Interest_Expense

Net Interest Expense	12 Months Ended
	Mar. 31, 2015
Banking And Thrift Interest [Abstract]
Net Interest Expense	(K) Net Interest Expense
	The following components are included in interest expense, net:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Interest Income	$	(6	)	$	(5	)	$	(53	)
	Interest Expense		14,768			16,751			14,769
	Interest Expense (Income) – IRS		(3,847	)		641			409
	Other Expenses		828			895			698
	Interest Expense, net	$	11,743		$	18,282		$	15,823
	Interest income includes interest on investments of excess cash. Components of interest expense include interest associated with the Senior Notes, Credit Facility and commitment fees based on the unused portion of the Credit Facility. Other expenses include amortization of debt issuance costs, and bank credit facility costs.
	Interest expense (income) – IRS relates to interest accrued on our unrecognized tax benefits, primarily related to the Republic Asset Acquisition. As noted in Footnote (H) of the Notes to Consolidated Financial Statements, our settlement with the IRS was finalized.  As a result of the settlement, we received approximately $4.4 million of interest related to penalties paid to the IRS related to the Republic Asset Acquisition.

Pension_and_Profit_Sharing_Pla

Pension and Profit Sharing Plans	12 Months Ended
	Mar. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Pension and Profit Sharing Plans	(L) Pension and Profit Sharing Plans
	We have several defined benefit and defined contribution retirement plans which together cover substantially all of our employees. Benefits paid under the defined benefit plans covering certain hourly employees are based on years of service and the employee’s qualifying compensation over the last few years of employment. Our funding policy is to generally contribute amounts that are deductible for income tax purposes. The annual measurement date is March 31 for the benefit obligations, fair value of plan assets and the funded status of the defined benefit plans.
	The following table provides a reconciliation of the obligations and fair values of plan assets for all of our defined benefit plans over the two year period ended March 31, 2015 and a statement of the funded status as of March 31, 2015 and 2014:
			For the Years Ended March 31,
			2015				2014
			(dollars in thousands)
	Reconciliation of Benefit Obligations -
	Benefit Obligation at April 1,	$		29,892			$	29,586
	Service Cost - Benefits Earned During the Period			874				1,129
	Interest Cost on Projected Benefit Obligation			1,278				1,222
	Amendments			805				-
	Actuarial (Gain) Loss			9,823				(1,237	)
	Benefits Paid			(881	)			(808	)
	Benefit Obligation at March 31,		$	41,791			$	29,892
	Reconciliation of Fair Value of Plan Assets -
	Fair Value of Plan Assets at April 1,		$	21,189			$	18,693
	Actual Return on Plan Assets			937				1,735
	Employer Contributions			810				1,569
	Benefits Paid			(881	)			(808	)
	Fair Value of Plans at March 31,			22,055				21,189
	Funded Status -
	Unfunded Status at March 31,		$	(19,736	)		$	(8,703	)
	Amounts Recognized in the Balance Sheet Consist of -
	Accrued Benefit Liability		$	(19,736	)		$	(8,703	)
	Accumulated Other Comprehensive Losses:
	Net Actuarial Loss			18,376				8,419
	Prior Service Cost			809				15
	Accumulated Other Comprehensive Losses		$	19,185			$	8,434
	Tax impact			(7,118	)			(2,952	)
	Accumulated Other Comprehensive Losses, net of tax		$	12,067			$	5,482
	Information for pension plans with an accumulated benefit obligation in excess of plan assets:
			March 31,
			2015				2014
			(dollars in thousands)
	Projected Benefit Obligation		$	41,791			$	29,892
	Accumulated Benefit Obligation		$	41,790			$	29,827
	Fair Value of Plan Assets		$	22,055			$	21,189
	Net periodic pension cost for the fiscal years ended March 31, 2015, 2014 and 2013, included the following components:
			For the Years Ended March 31,
			2015				2014			2013
			(dollars in thousands)
	Service Cost - Benefits Earned During the Period		$	874			$	1,129		$	785
	Interest Cost of Projected Benefit Obligation			1,278				1,222			1,222
	Expected Return on Plan Assets			(1,680	)			(1,506	)		(1,371	)
	Recognized Net Actuarial Loss			609				921			980
	Amortization of Prior-Service Cost			11				11			21
	Net Periodic Pension Cost		$	1,092			$	1,777		$	1,637
	We amended one of our pension plans during March 2015, which increased our prior service cost by approximately $0.8 million.  This amount is included in other comprehensive income and will be recognized in our statement of earnings as pension expense over the next three fiscal years.
	Expected benefit payments over the next five years, and the following five years under the pension plans are expected to be as follows (in thousands):
	Fiscal Years		Total
	2016		$	1,115
	2017		$	1,167
	2018		$	1,219
	2019		$	1,302
	2020		$	1,389
	2021-2025		$	8,908
	The following table sets forth the assumptions used in the actuarial calculations of the present value of net periodic benefit cost and benefit obligations:
			March 31,
			2015				2014			2013
	Net Periodic Benefit Costs -
	Discount Rate			4.41		%		4.2	%		4.56	%
	Expected Return on Plan Assets			8		%		8	%		8	%
	Rate of Compensation Increase			3.5		%		3.5	%		3.5	%
			March 31,
		2015				2014
Benefit Obligations -
Discount Rate			3.70%				4.41	%
Rate of Compensation Increase			3.50%				3.5	%
The expected long-term rate of return on plan assets is an assumption reflecting the anticipated weighted-average rate of earnings on the portfolio over the long-term. To arrive at this rate, we developed estimates of the key components underlying capital asset returns including: market-based estimates of inflation, real risk-free rates of return, yield curve structure, credit risk premiums and equity risk premiums. As appropriate, these components were used to develop benchmark estimates of the expected long-term management approach employed by us, and a return premium was added to the weighted-average benchmark portfolio return.
The pension plans’ approximate weighted-average asset allocation at March 31, 2015 and 2014 and the range of target allocation are as follows:
		Range of				Percentage of Plan
		Target				Assets at March 31,
		Allocation				2015			2014
Asset Category -
Equity Securities			40 – 60	%			61%			65%
Debt Securities			35 – 60	%			36%			30%
Other			0 – 5	%			3%			5%
Total							100%			100%
Our pension investment strategies have been developed as part of a comprehensive asset/liability management process that considers the interaction between both the assets and liabilities of the plan. These strategies consider not only the expected risk and returns on plan assets, but also the detailed actuarial projections of liabilities as well as plan-level objectives such as projected contributions, expense and funded status.
The principal pension investment strategies include asset allocation and active asset management. The range of target asset allocations have been determined after giving consideration to the expected returns of each asset class, the expected variability or volatility of the asset class returns over time, and the complementary nature or correlation of the asset classes within the portfolio. We also employ an active management approach for the portfolio. Each asset class is managed by one or more external money managers with the objective of generating returns, net of management fees that exceed market-based benchmarks. None of the plans hold any EXP stock.
Based on our current actuarial estimates, we anticipate making contributions ranging from approximately $0.5 million to $1.0 million to our defined benefit plans for fiscal year 2015.
The fair values of our defined benefit plans’ consolidated assets by category as of March 31, 2015 and 2014 were as follows:
		March 31,
		2015				2014
		(dollars in thousands)
Equity Securities		$	13,510			$	13,973
Fixed Income Securities			7,985				6,526
Real Estate Funds			133				130
Commodity Linked Funds			124				170
Cash Equivalents			303				390
Total		$	22,055			$	21,189
The fair values of our defined benefit plans’ consolidated assets were determined using the fair value hierarchy of inputs described in Note (A).
The fair values by category of inputs as of March 31, 2015 were as follows:
Asset Categories		Quoted Prices in				Significant			Significant			Total
		Active Markets				Other			Unobservable
		for Identical				Observable			Inputs
		Assets				Inputs			(Level 3)
		(Level 1)				(Level 2)
		(dollars in thousands)
Equity Securities		$	—			$	13,510		$	—		$	13,510
Fixed Income Securities			—				7,985			—			7,985
Real Estate Funds			—				133			—			133
Commodity Linked Funds			—				124			—			124
Cash Equivalents			303				—			—			303
		$	303			$	21,752		$	—		$	22,055
The fair values by category of inputs as of March 31, 2014 were as follows:
Asset Categories		Quoted Prices in				Significant Other			Significant				Total
		Active Markets				Observable			Unobservable
		for Identical				Inputs			Inputs
		Assets				(Level 2)			(Level 3)
		(Level 1)
		(dollars in thousands)
Equity Securities		$	—			$	13,973		$	—		$	13,973
Fixed Income Securities			—				6,526			—			6,526
Real Estate Funds			—				130			—			130
Commodity Linked Funds			—				170			—			170
Cash Equivalents			390				—			—			390
		$	390			$	20,799		$	—		$	21,189
Equity securities consist of funds that are not actively traded. These funds are maintained by an investment manager and are primarily invested in indexes. The remaining funds, excluding cash, primarily consist of investments in institutional funds.
We also provide profit sharing plans, which cover substantially all salaried and certain hourly employees. The profit sharing plan is a defined contribution plan funded by employer discretionary contributions and also allows employees to contribute a certain percentage of their base annual salary. Employees are fully vested to the extent of their contributions and become fully vested in any Company contributions over a six year period for salaried employees and a three year period for hourly employees. Costs relating to the employer discretionary contributions for our contribution plan totaled $5.3 million, $4.5 million and $3.3 million in fiscal years 2015, 2014 and 2013, respectively.
Employees who became employed by us as a result of a previous transaction are provided benefits substantially comparable to those provided under the seller’s benefit plans. These plans included the seller’s 401(k) plan which included employer matching percentages for hourly employees. As a result, we made matching contributions to the hourly profit sharing plan totaling $0.2 million, $0.2 million and $0.1 million for these employees during fiscal years 2015, 2014 and 2013, respectively.
Approximately sixty of our employees belong to five different multi-employer plans. The collective bargaining agreements for the employees who participate in the multi-employer plans expire between June 2015 and March 2017. Our expense related to these plans was approximately $1.0 million, $1.0 million and $0.2 million during fiscal years 2015, 2014 and 2013, respectively. We anticipate the total expense in fiscal 2016 related to these plans will be approximately $1.0 million.

Quarterly_Results_unaudited

Quarterly Results (unaudited)	12 Months Ended
	Mar. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results (unaudited)	(M) Quarterly Results (unaudited)
		For the Years Ended March 31,
		2015		2014
		(dollars in thousands, except per share data)
	First Quarter -
	Revenues	$	266,251	$	227,044
	Gross Profit		56,401		46,604
	Earnings Before Income Taxes		55,786		44,516
	Net Earnings		37,710		30,101
	Diluted Earnings Per Share	$	0.75	$	0.6
	Second Quarter -
	Revenues	$	284,808	$	252,646
	Gross Profit		75,061		59,479
	Earnings Before Income Taxes		74,577		58,688
	Net Earnings		50,319		39,903
	Diluted Earnings Per Share	$	1	$	0.8
	Third Quarter -
	Revenues	$	291,529	$	228,812
	Gross Profit		79,149		49,848
	Earnings Before Income Taxes		77,866		48,833
	Net Earnings		52,030		31,621
	Diluted Earnings Per Share	$	1.03	$	0.63
	Fourth Quarter -
	Revenues	$	223,780	$	189,894
	Gross Profit		43,522		29,528
	Earnings Before Income Taxes		44,698		29,767
	Net Earnings		46,794		22,618
	Diluted Earnings Per Share	$	0.93	$	0.45
	The fourth quarter of fiscal 2015 was favorably impacted by the settlement agreement with the IRS.  As a result of the settlement agreement, we recorded an income tax benefit of approximately $17 million, including state benefits.  The related interest of approximately $4.4 million was also recorded during the fourth quarter of fiscal 2015.  The fourth quarter of fiscal 2015 was adversely impacted by certain acquisition related expenses primarily due to diligence efforts at growing our construction products business and litigation costs related to the settlement of our lawsuit with the IRS.  The total impact of these expenses was approximately $4.1 million.
	The fourth quarter of fiscal 2014 was adversely impacted by the annual maintenance outage of approximately $4.5 million at our Illinois cement plant. This outage has historically occurred in April or May of the fiscal year. The fourth quarter of fiscal 2014 was also adversely impacted by approximately $1.3 million in legal costs, $1.5 million in maintenance, and $0.9 million in increased natural gas costs for our gypsum wallboard business. The increase in maintenance costs was due to the timing of certain major maintenance projects, while the increase in natural gas was due to increased market prices.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	12 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation –
	The consolidated financial statements include the accounts of Eagle Materials Inc. and its majority-owned subsidiaries (“EXP” or the “Company”), which may be referred to as “our”, “we”, or “us”. All intercompany balances and transactions have been eliminated. EXP is a holding company whose assets consist of its investments in its subsidiaries, joint venture, intercompany balances and holdings of cash and cash equivalents. The businesses of the consolidated group are conducted through EXP’s subsidiaries. The Company conducts one of its cement plant operations through a joint venture, Texas Lehigh Cement Company L.P., which is located in Buda, Texas (the “Joint Venture”). Investments in the Joint Venture and affiliated companies owned 50% or less are accounted for using the equity method of accounting. The Equity in Earnings of Unconsolidated Joint Venture has been included for the same period as our March 31 year end.
	The preparation of financial statements in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Reclassifications	Reclassifications – Certain reclassifications have been made to the prior year to conform to the current year presentation.
Cash and Cash Equivalents	Cash and Cash Equivalents –
	Cash equivalents include short-term, highly liquid investments with original maturities of three months or less and are recorded at cost, which approximates market value.
Accounts and Notes Receivable	Accounts and Notes Receivable –
	Accounts and notes receivable have been shown net of the allowance for doubtful accounts of $7.1 million and $5.8 million at March 31, 2015 and 2014, respectively. We perform ongoing credit evaluations of our customers’ financial condition and generally require no collateral from our customers. The allowance for non-collection of receivables is based upon analysis of economic trends in the construction and oil and gas industries, detailed analysis of the expected collectability of accounts receivable that are past due and the expected collectability of overall receivables. We have no significant credit risk concentration among our diversified customer base.
	We had notes receivable totaling approximately $3.3 million at March 31, 2015, of which approximately $0.5 million has been classified as current and presented with accounts receivable on the balance sheet. We lend funds to certain companies in the ordinary course of business, and the notes bear interest, on average, at 3.9%, which will vary based on changes to LIBOR. Remaining unpaid amounts, plus accrued interest, mature on various dates between 2015 and 2017. The notes are collateralized by certain assets of the borrowers, namely property and equipment. We monitor the credit risk of each borrower by focusing on the timeliness of payments, review of credit history and credit metrics and interaction with the borrowers. At March 31, 2015 and 2014, approximately $0.3 million of our allowance for doubtful accounts is related to our notes receivable.
Inventories	Inventories –
	Inventories are stated at the lower of average cost (including applicable material, labor, depreciation, and plant overhead) or market. Inventories consist of the following:
		March 31,
		2015			2014
		(dollars in thousands)
	Raw Materials and Materials-in-Progress	$	115,345		$	82,319
	Finished Cement		20,508			19,173
	Gypsum Wallboard		7,741			7,144
	Paperboard		8,493			4,102
	Frac Sand		4,928			275
	Aggregates		11,131			11,815
	Repair Parts and Supplies		62,121			56,119
	Fuel and Coal		5,197			6,149
		$	235,464		$	187,096
Property, Plant and Equipment	Property, Plant and Equipment –
	Property, plant and equipment are stated at cost. Major renewals and improvements are capitalized and depreciated. Annual maintenance is expensed as incurred. Depreciation is provided on a straight-line basis over the estimated useful lives of depreciable assets and totaled $69.7 million, $67.3 million and $55.1 million for the years ended March 31, 2015, 2014 and 2013, respectively. Raw material deposits are depleted as such deposits are extracted for production utilizing the units-of-production method. Costs and accumulated depreciation applicable to assets retired or sold are eliminated from the accounts and any resulting gains or losses are recognized at such time. The estimated lives of the related assets are as follows:
	Plants		20 to 30 years
	Buildings		20 to 40 years
	Machinery and Equipment		3 to 25 years
	We periodically evaluate whether current events or circumstances indicate that the carrying value of our depreciable assets may not be recoverable. At March 31, 2015 and 2014, management believes no events or circumstances indicate that the carrying value may not be recoverable.
	We idled our gypsum manufacturing facility in Bernalillo, N.M. in December 2009, due to cyclical low gypsum wallboard demand. The carrying value of the Bernalillo plant and equipment at March 31, 2015 was $2.7 million and $0.4 million, respectively, and we continue to depreciate the assets over their estimated useful life. We currently have a strong market position in New Mexico, and our Albuquerque gypsum wallboard facility is operating at close to capacity. We plan on resuming manufacturing at the Bernalillo facility in the future when additional capacity is needed to meet demand for our products. Costs of maintaining the facility during the idling are not significant, and the facility was generating positive cash flow prior to being idled; therefore, we have determined that the value of the plant and equipment is not impaired. We are not currently considering the permanent closure of the Bernalillo facility. Any decision to permanently close Bernalillo would be the result of future changes in the building materials industry in the southwest United States and Rocky Mountain region, including changes in the production capacity or operations of our competitors, demand for gypsum wallboard or general macro-economic conditions, which we do not foresee at the present time. If we were to permanently close the Bernalillo facility, or if our expectations as to its use changed such that we project the future undiscounted cash flows from its operations would be insufficient to recover its carrying value due to the factors described above, or for any other reason, we would recognize impairment at that time.
Impairment or Disposal of Long-Lived and Intangible Assets	Impairment or Disposal of Long-Lived and Intangible Assets –
	We evaluate the recoverability of our long-lived assets and certain identifiable intangibles, such as permits and customer contracts, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets, such as plants, buildings and machinery and equipment, including mining assets, is measured by comparing the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. Such evaluations for impairment are significantly impacted by estimates of future prices for our products, capital needs, economic trends in the construction sector and other factors. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds their fair value. Assets to be disposed of by sale are reflected at the lower of their carrying amount or fair value less cost to sell.
Goodwill and Intangible Assets	Goodwill and Intangible Assets –
	Goodwill: Goodwill is subject to at least an annual assessment for impairment by applying a fair-value-based test. We have elected to test for goodwill impairment in the fourth quarter of each fiscal year. The goodwill impairment test is a two-step process, which requires us to make judgments in determining what assumptions to use in the calculation. The first step of the process consists of estimating the fair value of each reporting unit based on a discounted cash flow model using revenues and profit forecasts and comparing those estimated fair values with the carrying value; a second step is performed, if necessary, to compute the amount of the impairment by determining an “implied fair value” of goodwill. Similar to the review for impairment of other long-lived assets, evaluations for impairment are significantly impacted by estimates of future prices for our products, capital needs, economic trends and other factors.
	Intangible Assets: Intangible assets at March 31, 2015 and 2014 consist of the following:
		March 31, 2015
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		5-15 years		$	62,060		$	(5,994	)	$	56,066
	Sales contracts		4 years			2,500			(1,458	)		1,042
	Permits		40 years			27,440			(5,896	)		21,544
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	224,515		$	(13,348	)	$	211,167
		March 31, 2014
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		15 years		$	6,060		$	(1,580	)	$	4,480
	Sales contracts		4 years			2,500			(833	)		1,667
	Permits		40 years			27,240			(5,212	)		22,028
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	168,315		$	(7,625	)	$	160,690
	Amortization expense of intangibles was $5.7 million, $1.7 million and $1.0 million for the years ended March 31, 2015, 2014 and 2013, respectively. Amortization expense is expected to be approximately $13.4 million per year for fiscal year 2016, $13.2 million for fiscal year 2017, $12.7 million for fiscal year 2018, $12.6 million for fiscal year 2019 and $6.2 million for fiscal year 2020.
Other Assets	Other Assets –
	Other assets are primarily composed of loan fees and financing costs, deferred expenses, and deposits.
Income Taxes	Income Taxes –
	Income taxes are accounted for using the asset and liability method. Deferred taxes are recognized for the tax consequences of temporary differences by applying enacted statutory tax rates applicable to future years to differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities. The effect on deferred taxes of a change in tax rates is recognized in earnings in the period that includes the enactment date. In addition, we recognize future tax benefits to the extent that such benefits are more likely than not to be realized.
Stock Repurchases	Stock Repurchases –
	Our Board of Directors has approved the repurchase of a cumulative total of 31,610,605 shares, of which approximately 717,300 shares remain available for repurchase at March 31, 2015. We did not repurchase any shares in the open market during the years ended March 31, 2015, 2014 and 2013.
Revenue Recognition	Revenue Recognition –
	Revenue from the sale of cement, gypsum wallboard, paperboard, frac sand, concrete and aggregates is recognized when title and ownership are transferred upon shipment to the customer. Fees for shipping and handling are recorded as revenue, while costs incurred for shipping and handling are recorded as expenses.
	We classify amounts billed to customers for freight as revenues and freight costs as cost of goods sold, respectively, in the Consolidated Statements of Earnings. Approximately $124.0 million, $113.1 million and $83.2 million were classified as cost of goods sold in the years ended March 31, 2015, 2014 and 2013, respectively.
	Other income (loss) includes lease and rental income, asset sale income, non-inventoried aggregates sales income, distribution center income and trucking income as well as other miscellaneous revenue items and costs which have not been allocated to a business segment.
Comprehensive Income/Losses	Comprehensive Income/Losses –
	As of March 31, 2015, we have an accumulated other comprehensive loss of $12.1 million, which is net of income taxes of $7.1 million, in connection with recognizing the difference between the fair value of the pension assets and the projected benefit obligation.
Consolidated Cash Flows - Supplemental Disclosures	Consolidated Cash Flows – Supplemental Disclosures –
	Interest payments made during the years ended March 31, 2015, 2014 and 2013 were $15.1 million, $17.0 million and $14.6 million, respectively.
Statements of Consolidated Earnings - Supplemental Disclosures	Statements of Consolidated Earnings – Supplemental Disclosures –
	Maintenance and repair expenses are included in each segment’s costs and expenses. We incurred $86.7 million, $77.4 million and $61.3 million in the years ended March 31, 2015, 2014 and 2013, respectively, which is included in Cost of Goods Sold on the Consolidated Statement of Earnings.
	Selling, general and administrative expenses of the operating units are included in Cost of Goods Sold on the Consolidated Statements of Earnings. Corporate general and administrative (“G&A”) expenses include administration, financial, legal, employee benefits and other corporate activities and are shown separately in the consolidated statements of earnings. Corporate G&A also includes stock compensation expense. See Note (J), Stock Option Plans, for more information.
	Total selling, general and administrative expenses for each of the periods are summarized as follows:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Operating Units Selling, G&A	$	49,326		$	50,175		$	39,133
	Corporate G&A		30,751			24,552			23,918
		$	80,077		$	74,727		$	63,051
Earnings Per Share	Earnings Per Share –
		For the Years Ended March 31,
		2015			2014			2013
	Weighted-Average Shares of Common Stock Outstanding					49,090,750			46,622,646
			49,604,249
	Effect of Dilutive Shares:
	Assumed Exercise of Outstanding Dilutive Options		1,350,556			1,574,491			1,984,563
	Less Shares Repurchased from Proceeds of Assumed Exercised Options		(868,636	)		(1,032,359	)		(1,568,604	)
	Restricted Stock Units		286,074			306,283			301,845
	Weighted-Average Common Stock and Dilutive Securities Outstanding		50,372,243			49,939,165			47,340,450
	The “Less Shares Repurchased from Proceeds of Assumed Exercised Options” line includes unearned compensation related to outstanding stock options.
	There were 285,267, 146,696 and 1,082,380 stock options at an average exercise price of $82.72 per share, $65.12 per share and $39.65 per share that were excluded from the computation of diluted earnings per share for the years ended March 31, 2015, 2014 and 2013, respectively, because such inclusion would have been anti-dilutive.
Fair Value Measures	Fair Value Measures –
	Certain assets and liabilities are required to be recorded or disclosed at fair value. The estimated fair values of those assets and liabilities have been determined using market information and valuation methodologies. Changes in assumptions or estimation methods could affect the fair value estimates; however, we do not believe any such changes would have a material impact on our financial condition, results of operations or cash flows. There are three levels of inputs that may be used to measure fair value:
	Level 1 – Quoted prices for identical assets and liabilities in active markets;
	Level 2 – Quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data; and
	Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets and liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.
New Accounting Standards	New Accounting Standards –
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers.” ASU 2014-09 supersedes the revenue recognition requirements in “Revenue Recognition (Topic 605),” and requires entities to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The standard will be effective for us in the first quarter of fiscal 2018, with early adoption not permitted. There are two transition methods available under the new standard, either cumulative effect or retrospective. We are currently evaluating the impact of this ASU and have not yet selected a transition method.
	In April 2015, The Financial Accounting Standards Board issued ASU 2015-03, “Interest-Imputation of Interest (Subtopic 830-30). This standard requires that discounts, premiums or debt issue costs related to borrowings be reported in the balance sheet as a direct reduction of the associated borrowing. The standard will be effective for us in the first quarter of fiscal 2017, and earlier application is permitted for financial statements that have not been previously issued.  The impact of adopting this ASU is not expected to be material.
Acquisition and Litigation Expense	Acquisition and Litigation Expense
	Acquisition and litigation expense consists primarily of expenses incurred during our acquisition, as discussed in Note (B), CRS Acquisition, and significant legal expenses incurred during litigation primarily involving the lawsuit against the Internal Revenue Service (“IRS”). See Note (H), Income Taxes, for more information about the outstanding lawsuit with the IRS.

Significant_Accounting_Policie2

Significant Accounting Policies (Tables)	12 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Schedule Of Inventories	Inventories consist of the following:
		March 31,
		2015			2014
		(dollars in thousands)
	Raw Materials and Materials-in-Progress	$	115,345		$	82,319
	Finished Cement		20,508			19,173
	Gypsum Wallboard		7,741			7,144
	Paperboard		8,493			4,102
	Frac Sand		4,928			275
	Aggregates		11,131			11,815
	Repair Parts and Supplies		62,121			56,119
	Fuel and Coal		5,197			6,149
		$	235,464		$	187,096
Schedule of Property, Plant and Equipment Estimated Lives	The estimated lives of the related assets are as follows:
	Plants		20 to 30 years
	Buildings		20 to 40 years
	Machinery and Equipment		3 to 25 years
Schedule of Goodwill and Intangible Assets	Intangible assets at March 31, 2015 and 2014 consist of the following:
		March 31, 2015
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		5-15 years		$	62,060		$	(5,994	)	$	56,066
	Sales contracts		4 years			2,500			(1,458	)		1,042
	Permits		40 years			27,440			(5,896	)		21,544
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	224,515		$	(13,348	)	$	211,167
		March 31, 2014
		Amortization			Cost			Accumulated			Net
		Period						Amortization
		(dollars in thousands)
	Intangible Assets and Goodwill:
	Customer contracts and relationships		15 years		$	6,060		$	(1,580	)	$	4,480
	Sales contracts		4 years			2,500			(833	)		1,667
	Permits		40 years			27,240			(5,212	)		22,028
	Goodwill					132,515			—			132,515
	Total intangible assets and goodwill				$	168,315		$	(7,625	)	$	160,690
Schedule of Total Selling, General and Administrative Expenses	Total selling, general and administrative expenses for each of the periods are summarized as follows:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Operating Units Selling, G&A	$	49,326		$	50,175		$	39,133
	Corporate G&A		30,751			24,552			23,918
		$	80,077		$	74,727		$	63,051
Schedule Of Earnings Per Share
		For the Years Ended March 31,
		2015			2014			2013
	Weighted-Average Shares of Common Stock Outstanding					49,090,750			46,622,646
			49,604,249
	Effect of Dilutive Shares:
	Assumed Exercise of Outstanding Dilutive Options		1,350,556			1,574,491			1,984,563
	Less Shares Repurchased from Proceeds of Assumed Exercised Options		(868,636	)		(1,032,359	)		(1,568,604	)
	Restricted Stock Units		286,074			306,283			301,845
	Weighted-Average Common Stock and Dilutive Securities Outstanding		50,372,243			49,939,165			47,340,450

CRS_Acquisition_Tables

CRS Acquisition (Tables)	12 Months Ended
	Mar. 31, 2015
Business Combinations [Abstract]
Components of Purchase Price Allocation	The following table summarizes the provisional allocation of the estimated Purchase Price to assets acquired and liabilities assumed as of the acquisition date:
	Purchase price allocation at acquisition date (in thousands)	As of
		November 14, 2014
	Cash and cash equivalents	$	219
	Accounts Receivable		14,640
	Inventories		9,627
	Prepaid and Other Assets		753
	Property and Equipment		192,738
	Intangible Assets		56,200
	Indemnity under Sales Agreement		14,810
	Other Assets		1,120
	Accounts Payable		(4,343	)
	Accrued Liabilities		(2,585	)
	Obligations under Long-term Sales Agreements		(28,131	)
	Asset Retirement Obligation		(4,112	)
	Deferred Taxes		(13,765	)
	Total Net Assets		237,171
	Goodwill		—
	Total Estimated Purchase Price	$	237,171
Summary of Fair Value Estimates of Identifiable Intangible Assets and Weighted-Average Useful Lives	The following table is a summary of the fair value estimates of the identifiable intangible assets (in thousands) and their weighted-average useful lives:
		Weighted			Estimated
		Average Life			Fair Value
	Customer Relationships		4			56,000
	Permits		40			200
	Total Intangible Assets				$	56,200
Net Sales and Operating Loss of CRS Proppants	The following table presents the net sales and operating loss of CRS Proppants that has been included in our consolidated statement of earnings from November 14, 2014 through the end of the fiscal year:
		Fiscal Year Ended
		March 31, 2015
		(dollars in thousands)
	Revenues	$	28,035
	Operating Loss	$	5,002
Unaudited Pro Forma Results
		For the Fiscal Year Ended
		March 31,
		2015			2014
		(dollars in thousands)
	Revenues	$	1,124,755		$	961,006
	Net Income	$	188,715		$	107,764
	Earnings per share – basis	$	3.8		$	2.2
	Earnings per share - diluted	$	3.75		$	2.16

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Mar. 31, 2015
Property Plant And Equipment [Abstract]
Schedule of Property, Plant and Equipment	Cost by major category and accumulated depreciation are summarized as follows:
		March 31,
		2015			2014
		(dollars in thousands)
	Land and Quarries	$	345,991		$	171,987
	Plants		1,378,497			1,357,594
	Buildings, Machinery and Equipment		151,627			111,263
	Construction in Progress		86,100			20,131
			1,962,215			1,660,975
	Accumulated Depreciation		(740,396	)		(676,924	)
		$	1,221,819		$	984,051

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Mar. 31, 2015
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses at March 31, 2015 and 2014 consist of the following:
		March 31,
		2015		2014
		(dollars in thousands)
	Payroll and Incentive Compensation	$	19,082	$	12,855
	Benefits		9,951		10,158
	Interest		4,524		4,813
	Property Taxes		3,189		2,801
	Power and Fuel		1,619		2,132
	Legal		1,673		1,831
	Sales and Use Tax		523		658
	Acquisition Related Expenses		1,355		—
	Other		4,914		6,272
		$	46,830	$	41,520

Indebtedness_Tables

Indebtedness (Tables)	12 Months Ended
	Mar. 31, 2015
Debt Instrument [Line Items]
Long-Term Debt	Long-term debt consists of the following:
		As of
		March 31,			March 31,
		2015			2014
		(dollars in thousands)
	Bank Credit Facility	$	330,000		$	189,000
	Senior Notes		182,759			192,259
	Total Debt		512,759			381,259
	Less: Current Portion of Long-term Debt		(57,045	)		(9,500	)
	Long-term Debt	$	455,714		$	371,759
Schedule of Maturities of Long-Term Debt	Our maturities of long-term debt during the next five fiscal years and thereafter are as follows:
	Fiscal Year	Amount
	2016	$	57,045
	2017		8,000
	2018		81,214
	2019		—
	2020		366,500
	Thereafter		—
	Total	$	512,759
2005 Note Purchase Agreement [Member]
Debt Instrument [Line Items]
Amount Outstanding of Tranches	Following these repurchases, the amounts outstanding for each of the remaining tranches are as follows:
		Principal			Maturity Date			Interest Rate
	Tranche B	$	57.0 million			15-Nov-15			5.38	%
	Tranche C	$	57.2 million			15-Nov-17			5.48	%
2007 Note Purchase Agreement [Member]
Debt Instrument [Line Items]
Amount Outstanding of Tranches	Following these repurchases and maturation, the amounts outstanding for each of the four tranches are as follows:
		Principal			Maturity Date			Interest Rate
	Tranche B	$	8.0 million			2-Oct-16			6.27	%
	Tranche C	$	24.0 million			2-Oct-17			6.36	%
	Tranche D	$	36.5 million			2-Oct-19			6.48	%

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Senior Notes	The fair value of our senior notes has been estimated based upon our current incremental borrowing rates for similar types of borrowing arrangements. The fair value of our Senior Notes at March 31, 2015 is as follows:
		Fair Value
		(dollars in thousands)
	Series 2005A Tranche B	$	58,206
	Series 2005A Tranche C		60,911
	Series 2007A Tranche B		8,434
	Series 2007A Tranche C		25,952
	Series 2007A Tranche D		40,777

Business_Segments_Tables

Business Segments (Tables)	12 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Financial Information Related to Operations by Segment	The following table sets forth certain financial information relating to our operations by segment
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Revenues -
	Cement		$	488,644		$	438,224		$	304,125
	Gypsum Wallboard			437,514			387,016			306,529
	Paperboard			142,690			130,178			121,930
	Oil and Gas Proppants			81,381			19,557			—
	Concrete and Aggregates			107,892			96,908			56,287
				1,258,121			1,071,883			788,871
	Less: Intersegment Revenues			(65,533	)		(62,094	)		(49,987	)
	Less: Joint Venture Revenues			(126,220	)		(111,393	)		(96,322	)
			$	1,066,368		$	898,396		$	642,562
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Intersegment Revenues -
	Cement		$	9,598		$	8,952		$	2,850
	Paperboard			55,060			52,119			46,393
	Concrete and Aggregates			875			1,023			744
			$	65,533		$	62,094		$	49,987
	Cement Sales Volumes (M tons) -
	Wholly-Owned			3,744			3,580			2,390
	Joint Venture			1,055			1,013			913
				4,799			4,593			3,303
			For the Years Ended March 31,
			2015			2014			2013
			(dollars in thousands)
	Operating Earnings -
	Cement	$		117,527		$	89,486		$	46,228
	Gypsum Wallboard			145,871			114,852			69,712
	Paperboard			31,512			23,610			25,200
	Oil and Gas Proppants			(2,546	)		(4,890	)		(1,253	)
	Concrete and Aggregates			6,736			212			(5,388	)
	Other, net			3,201			1,368			21
	Sub-Total			302,301			224,638			134,520
	Corporate General and Administrative			(30,751	)		(24,552	)		(23,918	)
	Acquisition, Litigation and Other Expense			(6,880	)		—			(10,683	)
	Earnings Before Interest and Income Taxes			264,670			200,086			99,919
	Interest Expense, net			(11,743	)		(18,282	)		(15,823	)
	Earnings Before Income Taxes		$	252,927		$	181,804		$	84,096
	Cement Operating Earnings -
	Wholly-Owned		$	72,560		$	51,675		$	13,721
	Joint Ventures			44,967			37,811			32,507
			$	117,527		$	89,486		$	46,228
	Capital Expenditures -
	Cement		$	27,086		$	12,226		$	15,583
	Gypsum Wallboard			7,129			4,825			2,682
	Paperboard			1,888			3,354			804
	Oil and Gas Proppants			61,484			34,264			—
	Concrete and Aggregates			13,851			4,572			33,932
	Other, net			135			249			10
			$	111,573		$	59,490		$	53,011
	Depreciation , Depletion and Amortization -
	Cement		$	31,839		$	31,829		$	20,658
	Gypsum Wallboard			20,092			20,981			21,045
	Paperboard			8,251			8,716			8,824
	Oil and Gas Proppants			8,839			1,707			—
	Concrete and Aggregates			5,533			5,205			5,212
	Corporate and Other			1,745			1,583			1,111
			$	76,299		$	70,021		$	56,850
			As of March 31,
			2015			2014			2013
		(dollars in thousands)
Identifiable Assets
Cement		$	777,956		$	762,578		$	756,158
Gypsum Wallboard			403,279			412,566			425,866
Paperboard			123,519			125,045			129,226
Oil and Gas Proppants			455,572			92,199			48,929
Concrete and Aggregates			96,610			87,364			87,054
Other, net			25,655			31,777			29,000
		$	1,882,591		$	1,511,529		$	1,476,233
Segment Breakdown of Goodwill	The segment breakdown of goodwill at March 31, 2015 and 2014 is as follows:
			For the Years Ended March 31,
			2015			2014
			(dollars in thousands)
	Cement		$	8,359		$	8,359
	Gypsum Wallboard			116,618			116,618
	Paperboard			7,538			7,538
			$	132,515		$	132,515

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Components of Provision for Income Taxes	The provision for income taxes includes the following components:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Current Provision (Benefit) -
	Federal	$	62,424		$	49,604		$	19,108
	State		(2,155	)		2,211			1,089
			60,269			51,815			20,197
	Deferred Provision (Benefit) -
	Federal		(962	)		7,691			5,173
	State		6,767			(1,945	)		982
			5,805			5,746			6,155
	Provision for Income Taxes	$	66,074		$	57,561		$	26,352
Schedule of Effective Tax Rates Vary from Federal Statutory Rates	The effective tax rates vary from the federal statutory rates due to the following items:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Earnings Before Income Taxes	$	252,927		$	181,804		$	84,096
	Income Taxes at Statutory Rate	$	88,524		$	63,631		$	29,434
	Increases (Decreases) in Tax Resulting from -
	State Income Taxes, net		4,582			173			1,346
	Statutory Depletion in Excess of Cost		(4,367	)		(3,512	)		(3,110	)
	Domestic Production Activities Deduction		(6,853	)		(3,453	)		(1,895	)
	Meals and Entertainment Disallowance		647			503			337
	Penalties on Uncertain Tax Positions		—			213			215
	IRS Settlement		(16,559	)		—			—
	Other		100			6			25
	Provision for Income Taxes	$	66,074		$	57,561		$	26,352
	Effective Tax Rate		26%			32	%		31	%
Schedule of Deferred Income Tax Provision	The deferred income tax provision results from the following temporary differences in the recognition of revenues and expenses for tax and financial reporting purposes:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Excess Tax Depreciation and Amortization	$	2,259		$	6,875		$	7,038
	Bad Debts		(142	)		(224	)		(73	)
	Uniform Capitalization		1,296			(1,127	)		(14	)
	Accrual Changes		(611	)		(1,075	)		(1,169	)
	Uncertain Tax Position Accruals		—			213			173
	Prepaid Insurance		(331	)		424			—
	State Income Taxes, net		6,060			(1,319	)		1,130
	Long-term Incentive Compensation Plans		(1,792	)		(373	)		1,293
	Other		(934	)		1,033			(1,093	)
		$	5,805		$	5,746		$	6,155
Schedule of Components of Deferred Income Taxes	Components of deferred income taxes are as follows:
		March 31,
		2015			2014
		(dollars in thousands)
	Items Giving Rise to Deferred Tax Liabilities -
	Excess Tax Depreciation and Amortization	$	(153,045	)	$	(144,519	)
	Depletion		(18,374	)		(100	)
	Repair Parts		(3,376	)		(4,545	)
	State Income Taxes, net		(13,708	)		(7,648	)
	Other		(5,359	)		(9,125	)
	Total Deferred Tax Liabilities	$	(193,862	)	$	(165,937	)
	Items Giving Rise to Deferred Tax Assets -
	Accrual Changes	$	10,557		$	9,946
	Bad Debts		2,264			2,122
	Uniform Capitalization		835			2,131
	Deferred Revenue		4,382			—
	Long-term Incentive Compensation Plan		8,318			6,526
	Other		7,118			—
	Total Deferred Tax Assets	$	33,474		$	20,725
Schedule of Income Taxes Classified in Consolidated Balance Sheet	Deferred income taxes are classified in the consolidated balance sheet as follows:
		March 31,
		2015			2014
		(dollars in thousands)
	Prepaid and Other Assets	$	2,265		$	561
	Deferred Income Taxes	$	(162,653	)	$	(145,773	)
Reconciliation of Consolidated Liability for Gross Unrecognized Tax Benefits	Reconciliation of the consolidated liability for gross unrecognized tax benefits, excluding interest, from April 1, 2012 to March 31, 2015, is as follows:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Balance at Beginning of Year	$	24,802		$	24,589		$	25,890
	Increase related to prior tax positions		—			213			215
	Decrease related to prior tax positions		(24,802	)		—			(1,516	)
	Payments		—			—			—
		$	—		$	24,802		$	24,589
Summary of Amounts of Interest and Penalties Recognized in Relation to Uncertain Tax Position	The following is a summary of the amounts of interest and penalties recognized in relation to our uncertain tax position:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Accrued interest recognized	$	(3,847	)	$	641		$	409
	Accrued penalties recognized	$	(6,475	)	$	213		$	173

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Mar. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Schedule of Minimum Annual Rental Commitments	Minimum annual rental commitments as of March 31, 2015, under noncancellable leases are set forth as follows (dollars in thousands):
	Fiscal Year	Amount
	2016	$	11,043
	2017	$	9,834
	2018	$	7,610
	2019	$	6,544
	2020	$	4,171
	Thereafter	$	13,758

Stock_Option_Plans_Tables

Stock Option Plans (Tables)	12 Months Ended
	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-Average Assumptions Used to Value Option Awards	The weighted-average assumptions used in the Black-Scholes model to value the option awards in fiscal 2015 and 2014 are as follows:
		2015			2014
	Dividend Yield		2	%		2	%
	Expected Volatility		44.8	%		44.6	%
	Risk Free Interest Rate		1.86	%		2.04	%
	Expected Life		6.0 years			7.0 years
Stock Option Activity	The following table represents stock option activity for the years presented:
		For the Years Ended March 31,
		2015						2014					2013
		Number			Weighted			Number			Weighted		Number			Weighted
		of			Average			of			Average		of			Average
		Shares			Exercise			Shares			Exercise		Shares			Exercise
					Price						Price					Price
	Outstanding Options at Beginning of Year		2,788,999		$	41.83			3,022,592		$	37.83		3,241,322		$	36.11
	Granted		297,151		$	86.41			256,989		$	68		569,679		$	34.64
	Exercised		(151,085	)	$	32.38			(485,582	)	$	29.72		(746,131	)	$	27.64
	Cancelled		(1,269,500	)	$	47.43			(5,000	)	$	53.22		(42,278	)	$	42.21
	Outstanding Options at End of Year		1,665,565		$	46.37			2,788,999		$	41.83		3,022,592		$	37.83
	Options Exercisable at End of Year		1,035,166						818,215					986,187
	Weighted Average Fair Value of Options Granted during the Year				$	32.31					$	26.35				$	13.28
Stock Options Outstanding
	The following table summarizes information about stock options outstanding at March 31, 2015:
		Options Outstanding									Options Exercisable
	Range of Exercise Prices	Number of			Weighted			Weighted			Number of		Weighted
		Shares			Average			Average			Shares		Average
		Outstanding			Remaining			Exercise			Outstanding		Exercise
					Contractual			Price					Price
					Life
	$23.17 - $30.74		592,210			4.19		$	26.5			589,210	$	26.48
	$33.08 - $40.78		487,968			6.91		$	33.95			308,352	$	34
	$53.22 - $74.10		283,236			7.82		$	66.58			118,089	$	66.59
	$79.90 - $93.56		302,151			9.31		$	86.42			19,515	$	91.71
			1,665,565			6.54		$	46.37			1,035,166	$	34.52

Net_Interest_Expense_Tables

Net Interest Expense (Tables)	12 Months Ended
	Mar. 31, 2015
Banking And Thrift Interest [Abstract]
Interest Expense, Net	The following components are included in interest expense, net:
		For the Years Ended March 31,
		2015			2014			2013
		(dollars in thousands)
	Interest Income	$	(6	)	$	(5	)	$	(53	)
	Interest Expense		14,768			16,751			14,769
	Interest Expense (Income) – IRS		(3,847	)		641			409
	Other Expenses		828			895			698
	Interest Expense, net	$	11,743		$	18,282		$	15,823

Pension_and_Profit_Sharing_Pla1

Pension and Profit Sharing Plans (Tables)	12 Months Ended
	Mar. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Schedule of Reconciliation of Obligations and Fair Values of Plan Assets	The following table provides a reconciliation of the obligations and fair values of plan assets for all of our defined benefit plans over the two year period ended March 31, 2015 and a statement of the funded status as of March 31, 2015 and 2014:
			For the Years Ended March 31,
			2015				2014
			(dollars in thousands)
	Reconciliation of Benefit Obligations -
	Benefit Obligation at April 1,	$		29,892			$	29,586
	Service Cost - Benefits Earned During the Period			874				1,129
	Interest Cost on Projected Benefit Obligation			1,278				1,222
	Amendments			805				-
	Actuarial (Gain) Loss			9,823				(1,237	)
	Benefits Paid			(881	)			(808	)
	Benefit Obligation at March 31,		$	41,791			$	29,892
	Reconciliation of Fair Value of Plan Assets -
	Fair Value of Plan Assets at April 1,		$	21,189			$	18,693
	Actual Return on Plan Assets			937				1,735
	Employer Contributions			810				1,569
	Benefits Paid			(881	)			(808	)
	Fair Value of Plans at March 31,			22,055				21,189
	Funded Status -
	Unfunded Status at March 31,		$	(19,736	)		$	(8,703	)
	Amounts Recognized in the Balance Sheet Consist of -
	Accrued Benefit Liability		$	(19,736	)		$	(8,703	)
	Accumulated Other Comprehensive Losses:
	Net Actuarial Loss			18,376				8,419
	Prior Service Cost			809				15
	Accumulated Other Comprehensive Losses		$	19,185			$	8,434
	Tax impact			(7,118	)			(2,952	)
	Accumulated Other Comprehensive Losses, net of tax		$	12,067			$	5,482
Schedule of Accumulated Benefit Obligation in Excess of Plan Assets	Information for pension plans with an accumulated benefit obligation in excess of plan assets:
			March 31,
			2015				2014
			(dollars in thousands)
	Projected Benefit Obligation		$	41,791			$	29,892
	Accumulated Benefit Obligation		$	41,790			$	29,827
	Fair Value of Plan Assets		$	22,055			$	21,189
Components of Net Periodic Cost	Net periodic pension cost for the fiscal years ended March 31, 2015, 2014 and 2013, included the following components:
			For the Years Ended March 31,
			2015				2014			2013
			(dollars in thousands)
	Service Cost - Benefits Earned During the Period		$	874			$	1,129		$	785
	Interest Cost of Projected Benefit Obligation			1,278				1,222			1,222
	Expected Return on Plan Assets			(1,680	)			(1,506	)		(1,371	)
	Recognized Net Actuarial Loss			609				921			980
	Amortization of Prior-Service Cost			11				11			21
	Net Periodic Pension Cost		$	1,092			$	1,777		$	1,637
Schedule of Expected Benefit Payments	Expected benefit payments over the next five years, and the following five years under the pension plans are expected to be as follows (in thousands):
	Fiscal Years		Total
	2016		$	1,115
	2017		$	1,167
	2018		$	1,219
	2019		$	1,302
	2020		$	1,389
	2021-2025		$	8,908
Schedule of Assumptions Used in Net Periodic Benefit Cost and Benefit Obligations	The following table sets forth the assumptions used in the actuarial calculations of the present value of net periodic benefit cost and benefit obligations:
			March 31,
			2015				2014			2013
	Net Periodic Benefit Costs -
	Discount Rate			4.41		%		4.2	%		4.56	%
	Expected Return on Plan Assets			8		%		8	%		8	%
	Rate of Compensation Increase			3.5		%		3.5	%		3.5	%
			March 31,
			2015				2014
	Benefit Obligations -
	Discount Rate			3.70%				4.41	%
	Rate of Compensation Increase			3.50%				3.5	%
Schedule of Pension Plans Weighted-Average Asset Allocation and Range of Target Allocation	The pension plans’ approximate weighted-average asset allocation at March 31, 2015 and 2014 and the range of target allocation are as follows:
			Range of				Percentage of Plan
			Target				Assets at March 31,
			Allocation				2015			2014
	Asset Category -
	Equity Securities			40 – 60	%			61%			65%
	Debt Securities			35 – 60	%			36%			30%
	Other			0 – 5	%			3%			5%
	Total							100%			100%
Schedule of Fair Values of Defined Benefit Plans	The fair values of our defined benefit plans’ consolidated assets by category as of March 31, 2015 and 2014 were as follows:
			March 31,
			2015				2014
			(dollars in thousands)
	Equity Securities		$	13,510			$	13,973
	Fixed Income Securities			7,985				6,526
	Real Estate Funds			133				130
	Commodity Linked Funds			124				170
	Cash Equivalents			303				390
	Total		$	22,055			$	21,189
Schedule of Fair Values of Defined Benefit Plans Determined Using Fair Value Hierarchy of Inputs	The fair values by category of inputs as of March 31, 2015 were as follows:
	Asset Categories		Quoted Prices in				Significant			Significant			Total
			Active Markets				Other			Unobservable
			for Identical				Observable			Inputs
			Assets				Inputs			(Level 3)
			(Level 1)				(Level 2)
			(dollars in thousands)
	Equity Securities		$	—			$	13,510		$	—		$	13,510
	Fixed Income Securities			—				7,985			—			7,985
	Real Estate Funds			—				133			—			133
	Commodity Linked Funds			—				124			—			124
	Cash Equivalents			303				—			—			303
			$	303			$	21,752		$	—		$	22,055
	The fair values by category of inputs as of March 31, 2014 were as follows:
	Asset Categories		Quoted Prices in				Significant Other			Significant				Total
			Active Markets				Observable			Unobservable
			for Identical				Inputs			Inputs
			Assets				(Level 2)			(Level 3)
			(Level 1)
			(dollars in thousands)
	Equity Securities		$	—			$	13,973		$	—		$	13,973
	Fixed Income Securities			—				6,526			—			6,526
	Real Estate Funds			—				130			—			130
	Commodity Linked Funds			—				170			—			170
	Cash Equivalents			390				—			—			390
			$	390			$	20,799		$	—		$	21,189

Quarterly_Results_unaudited_Ta

Quarterly Results (unaudited) (Tables)	12 Months Ended
	Mar. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Results (unaudited)
		For the Years Ended March 31,
		2015		2014
		(dollars in thousands, except per share data)
	First Quarter -
	Revenues	$	266,251	$	227,044
	Gross Profit		56,401		46,604
	Earnings Before Income Taxes		55,786		44,516
	Net Earnings		37,710		30,101
	Diluted Earnings Per Share	$	0.75	$	0.6
	Second Quarter -
	Revenues	$	284,808	$	252,646
	Gross Profit		75,061		59,479
	Earnings Before Income Taxes		74,577		58,688
	Net Earnings		50,319		39,903
	Diluted Earnings Per Share	$	1	$	0.8
	Third Quarter -
	Revenues	$	291,529	$	228,812
	Gross Profit		79,149		49,848
	Earnings Before Income Taxes		77,866		48,833
	Net Earnings		52,030		31,621
	Diluted Earnings Per Share	$	1.03	$	0.63
	Fourth Quarter -
	Revenues	$	223,780	$	189,894
	Gross Profit		43,522		29,528
	Earnings Before Income Taxes		44,698		29,767
	Net Earnings		46,794		22,618
	Diluted Earnings Per Share	$	0.93	$	0.45

Significant_Accounting_Policie3

Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Significant Accounting Policies [Line Items]
Ownership percentage		50.00%
Allowance for doubtful accounts	$5,800,000	$7,100,000	$5,800,000
Notes receivable, total		3,300,000
Notes receivable, current		500,000
Notes Receivable basis spread on Prime rate		3.90%
Depreciable assets		69,700,000	67,300,000	55,100,000
Carrying value of plant		2,700,000
Carrying value of equipment		400,000
Amortization expense of intangibles		5,700,000	1,700,000	1,000,000
Amortization expense, expected, for fiscal years 2016		13,400,000
Amortization expense, expected, for fiscal years 2017		13,200,000
Amortization expense, expected, for fiscal years 2018		12,700,000
Amortization expense, expected, for fiscal years 2019		12,600,000
Amortization expense, expected, for fiscal years 2020		6,200,000
Stock repurchases approved by Board of Directors		31,610,605
Shares remain available for repurchase		717,300
Freight costs as cost of goods sold		124,000,000	113,100,000	83,200,000
Accumulated other comprehensive loss	5,482,000	12,067,000	5,482,000
Net of income taxes for accumulated other comprehensive loss		7,100,000
Interest payments		15,100,000	17,000,000	14,600,000
Income taxes paid		78,300,000	41,700,000	14,800,000
Maintenance and repair expenses	4,500,000	86,700,000	77,400,000	61,300,000
Stock options outstanding (in shares)		285,267	146,696	1,082,380
Stock options, average exercise price per share		$82.72	$65.12	$39.65
Notes Receivable [Member]
Significant Accounting Policies [Line Items]
Allowance for doubtful accounts	$300,000	$300,000	$300,000

Schedule_of_Inventories_Detail

Schedule of Inventories (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Inventory [Line Items]
Inventories	$235,464	$187,096
Raw Materials and Material-in-Progress [Member]
Inventory [Line Items]
Inventories	115,345	82,319
Finished Cement [Member]
Inventory [Line Items]
Inventories	20,508	19,173
Gypsum Wallboard [Member]
Inventory [Line Items]
Inventories	7,741	7,144
Paperboard [Member]
Inventory [Line Items]
Inventories	8,493	4,102
Frac Sand [Member]
Inventory [Line Items]
Inventories	4,928	275
Aggregates [Member]
Inventory [Line Items]
Inventories	11,131	11,815
Repair Parts and Supplies [Member]
Inventory [Line Items]
Inventories	62,121	56,119
Fuel and Coal [Member]
Inventory [Line Items]
Inventories	$5,197	$6,149

Schedule_of_Property_Plant_And

Schedule of Property, Plant And Equipment Estimated Lives (Detail)	12 Months Ended
	Mar. 31, 2015
Plants [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	20 years
Plants [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	30 years
Buildings [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	20 years
Buildings [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	40 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	3 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated lives of assets - (years)	25 years

Schedule_of_Goodwill_and_Intan

Schedule of Goodwill and Intangible Assets (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	($13,348)	($7,625)
Good will, Cost	132,515	132,515
Goodwill, Net	132,515	132,515
Total intangible assets and goodwill, Cost	224,515	168,315
Total intangible assets and goodwill, Net	211,167	160,690
Customer contracts and relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	62,060	6,060
Accumulated Amortization	-5,994	-1,580
Finite-Lived Intangible Assets, Net	56,066	4,480
Amortization Period (years)		15 years
Customer contracts and relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (years)	5 years
Customer contracts and relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (years)	15 years
Sales contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	2,500	2,500
Accumulated Amortization	-1,458	-833
Finite-Lived Intangible Assets, Net	1,042	1,667
Amortization Period (years)	4 years	4 years
Permits [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Cost	27,440	27,240
Accumulated Amortization	-5,896	-5,212
Finite-Lived Intangible Assets, Net	$21,544	$22,028
Amortization Period (years)	40 years	40 years

Schedule_of_Total_Selling_Gene

Schedule of Total Selling, General and Administrative Expenses (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]
Operating Units Selling, G&A	$49,326	$50,175	$39,133
Corporate G&A	30,751	24,552	23,918
Total selling, general and administrative expenses	$80,077	$74,727	$63,051

Schedule_of_Earnings_Per_Share

Schedule of Earnings Per Share (Detail)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Weighted Average Number Of Shares Outstanding Diluted Disclosure Items [Abstract]
Weighted-Average Shares of Common Stock Outstanding	49,604,249	49,090,750	46,622,646
Assumed Exercise of Outstanding Dilutive Options	1,350,556	1,574,491	1,984,563
Less Shares Repurchased from Proceeds of Assumed Exercised Options	-868,636	-1,032,359	-1,568,604
Restricted Stock Units	286,074	306,283	301,845
Weighted-Average Common Stock and Dilutive Securities Outstanding	50,372,243	49,939,165	47,340,450

CRS_Acquisition_Additional_Inf

CRS Acquisition - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended
	Nov. 14, 2014	Mar. 31, 2015	Mar. 31, 2015	Mar. 03, 2015
				T
Business Acquisition [Line Items]
Business acquisition purchase price	$237,200,000
In-process capital expenditures	8,900,000
Inventory acquired at fair value	9,627,000
Decrease in deferred tax liability		6,200,000
Increase in asset retirement obligation		3,600,000
Decrease in property, plant and equipment		10,900,000
Direct acquisition cost			1,100,000
Customer Relationships [Member]
Business Acquisition [Line Items]
Increase in customer relationship intangible asset		8,000,000
CRS Proppants [Member] | Operating Loss [Member]
Business Acquisition [Line Items]
Depreciation and amortization			6,400,000
Inventory acquired at fair value		1,500,000	1,500,000
Skyway Plant [Member]
Business Acquisition [Line Items]
Business acquisition purchase price				$30,000,000
Ground granulated blast furnace slag purchased				600,000

Components_of_Purchase_Price_A

Components of Purchase Price Allocation (Detail) (USD $)	Mar. 31, 2015	Nov. 14, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified
Business Combinations [Abstract]
Cash and cash equivalents		$219
Accounts Receivable		14,640
Inventories		9,627
Prepaid and Other Assets		753
Property and Equipment		192,738
Intangible Assets	56,200	56,200
Indemnity under Sales Agreement		14,810
Other Assets		1,120
Accounts Payable		-4,343
Accrued Liabilities		-2,585
Obligations under Long-term Sales Agreements		-28,131
Asset Retirement Obligation		-4,112
Deferred Taxes		-13,765
Total Net Assets		237,171
Goodwill	132,515		132,515
Total Estimated Purchase Price		$237,171

Summary_of_Fair_Value_Estimate

Summary of Fair Value Estimates of Identifiable Intangible Assets and Weighted-Average Useful Lives (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Nov. 14, 2014
Acquired Finite Lived Intangible Assets [Line Items]
Estimated Fair Value	$56,200	$56,200
Customer Relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Weighted Average Life	4 years
Estimated Fair Value	56,000
Permits [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Weighted Average Life	40 years
Estimated Fair Value	$200

Net_Sales_and_Operating_Loss_o

Net Sales and Operating Loss of CRS Proppants (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Business Acquisition Pro Forma Information Nonrecurring Adjustment [Line Items]
Revenues	$1,124,755	$961,006
Operating Loss	302,301	224,638	134,520
CRS Proppants [Member]
Business Acquisition Pro Forma Information Nonrecurring Adjustment [Line Items]
Revenues	28,035
Operating Loss	$5,002

Unaudited_Pro_Forma_Results_De

Unaudited Pro Forma Results (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Business Combinations [Abstract]
Revenues	$1,124,755	$961,006
Net Income	$188,715	$107,764
Earnings per share – basis	$3.80	$2.20
Earnings per share - diluted	$3.75	$2.16

Recovered_Sheet1

Schedule of Property, Plant and Equipment (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$1,962,215	$1,660,975
Accumulated Depreciation	-740,396	-676,924
Property, Plant and Equipment, net	1,221,819	984,051
Land And Quarries [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	345,991	171,987
Plants [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,378,497	1,357,594
Buildings Machinery And Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	151,627	111,263
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$86,100	$20,131

Schedule_of_Accrued_Expenses_D

Schedule of Accrued Expenses (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Accounts Payable And Accrued Liabilities Current [Abstract]
Payroll and Incentive Compensation	$19,082	$12,855
Benefits	9,951	10,158
Interest	4,524	4,813
Property Taxes	3,189	2,801
Power and Fuel	1,619	2,132
Legal	1,673	1,831
Sales and Use Tax	523	658
Acquisition Related Expenses	1,355
Other	4,914	6,272
Accrued expenses, total	$46,830	$41,520

LongTerm_Debt_Detail

Long-Term Debt (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Total Debt	$512,759	$381,259
Less: Current Portion of Long-term Debt	-57,045	-9,500
Long-term Debt	455,714	371,759
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Total Debt	330,000	189,000
Senior Notes [Member]
Debt Instrument [Line Items]
Total Debt	$182,759	$192,259

Indebtedness_Additional_Inform

Indebtedness - Additional Information (Detail) (USD $)	0 Months Ended	12 Months Ended	97 Months Ended	78 Months Ended	1 Months Ended
In Millions, unless otherwise specified	Oct. 30, 2014	Mar. 31, 2015	Mar. 31, 2015	Mar. 31, 2013	Oct. 31, 2014	Mar. 31, 2014	Nov. 15, 2005	Oct. 02, 2007
							Loan	Loan
Debt Instrument [Line Items]
Senior notes, permitted minimum aggregate principal amount prepayment without penalty		10.00%
Percentage of face value to be paid if notes are prepaid		100.00%
Senior notes, calculation of make-whole amount, description		Discounting the remaining scheduled payments of interest and principal of the Senior Notes being prepaid at a discount rate equal to the sum of 50 basis points
Discount on senior notes principal and interest		0.50%
Interest coverage ratio	250.00%
Unused line of credit commitment fee based on leverage ratio	0.10%
Borrowings outstanding under Credit Facility		$330	$330
Bank credit facility, borrowings available		160.8	160.8
Letter of credit facility		50	50
Letters of credit outstanding, amount		9.2	9.2
Maximum [Member]
Debt Instrument [Line Items]
Consolidated funded indebtedness ratio	350.00%
Unused line of credit commitment fee based on leverage ratio	0.35%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Variable margin	1.00%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument [Line Items]
Variable margin	2.25%
Federal Funds Effective Swap Rate | Minimum [Member]
Debt Instrument [Line Items]
Variable margin	0.00%
Federal Funds Effective Swap Rate | Maximum [Member]
Debt Instrument [Line Items]
Variable margin	1.25%
Bank Credit Facility [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		1.50%	1.50%	2.00%		1.90%
Interest rate of debt instrument		1.60%	1.60%			1.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, principal balance	500
Credit facility, maturity date	31-Oct-19
Credit facility, interest rate description		At the option of the Company, outstanding principal amounts on the Amended Credit Facility bear interest at a variable rate equal to (i) LIBOR, plus an agreed margin (ranging from 100 to 225 basis points), which is to be established quarterly based upon the Company’s ratio of consolidated EBITDA, defined as earnings before interest, taxes, depreciation and amortization, to the Company’s consolidated indebtedness (the “Leverage Ratio”), or (ii) an alternative base rate which is the higher of (a) the prime rate or (b) the federal funds rate plus 1/2% per annum plus an agreed margin (ranging from 0 to 125 basis points). Interest payments are payable, in the case of loans bearing interest at a rate based on the federal funds rate, quarterly, or in the case of loans bearing interest at a rate based on LIBOR, at the end of the LIBOR advance periods, which can be a period of up to nine months at the option of the Company. The Company is also required to pay a commitment fee on unused available borrowings under the Amended Credit Facility ranging from 10 to 35 basis points depending upon the Leverage Ratio.
Revolving Credit Facility [Member] | Scenario, Previously Reported
Debt Instrument [Line Items]
Credit facility, principal balance	400
Credit facility, maturity date	15-Dec-15
Line of Credit | Federal Funds Effective Swap Rate | Maximum [Member]
Debt Instrument [Line Items]
Variable margin	0.50%
Letter of Credit [Member]
Debt Instrument [Line Items]
Bank credit facility, one-time fee		0.13%
Senior Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		5.81%	5.81%	5.81%		5.81%
Interest rate of debt instrument		5.80%	5.80%			5.81%
2005 Note Purchase Agreement [Member]
Debt Instrument [Line Items]
Senior notes, sale							200
Number of tranches							3
Senior notes, repurchased amount			81.1
Senior notes, payment terms		Interest for each tranche of Notes is payable semi-annually on May 15 and November 15 of each year until all principal is paid for the respective tranche.
2007 Note Purchase Agreement [Member]
Debt Instrument [Line Items]
Senior notes, sale								200
Number of tranches								4
Senior notes, repurchased amount				122
Senior notes, payment terms		Interest for each tranche of Notes is payable semi-annually on April 2 and October 2 of each year until all principal is paid for the respective tranche.
2007 Note Purchase Agreement [Member] | Series 2007A Tranche A [Member]
Debt Instrument [Line Items]
Repayment of senior note					$9.50

Schedule_of_Maturities_of_Long

Schedule of Maturities of Long-Term Debt (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]
2016	$57,045
2017	8,000
2018	81,214
2020	366,500
Total	$512,759	$381,259

Amount_Outstanding_of_Tranches

Amount Outstanding of Tranches - Two Thousand Five Note Purchase Agreement (Detail) (2005 Note Purchase Agreement [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Series 2005A Tranche B [Member]
Debt Instrument [Line Items]
Principal	$57
Maturity Date	15-Nov-15
Interest Rate	5.38%
Series 2005A Tranche C [Member]
Debt Instrument [Line Items]
Principal	$57.20
Maturity Date	15-Nov-17
Interest Rate	5.48%

Amount_Outstanding_of_Tranches1

Amount Outstanding of Tranches - Two Thousand Seven Note Purchase Agreement (Detail) (2007 Note Purchase Agreement [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Series 2007A Tranche B [Member]
Debt Instrument [Line Items]
Principal	$8
Maturity Date	2-Oct-16
Interest Rate	6.27%
Series 2007A Tranche C [Member]
Debt Instrument [Line Items]
Principal	24
Maturity Date	2-Oct-17
Interest Rate	6.36%
Series 2007A Tranche D [Member]
Debt Instrument [Line Items]
Principal	$36.50
Maturity Date	2-Oct-19
Interest Rate	6.48%

Fair_Value_of_Senior_Notes_Det

Fair Value of Senior Notes (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Series 2005A Tranche B [Member]
Fair Value Of Financial Instruments [Line Items]
Fair Value of Senior Notes	$58,206
Series 2005A Tranche C [Member]
Fair Value Of Financial Instruments [Line Items]
Fair Value of Senior Notes	60,911
Series 2007A Tranche B [Member]
Fair Value Of Financial Instruments [Line Items]
Fair Value of Senior Notes	8,434
Series 2007A Tranche C [Member]
Fair Value Of Financial Instruments [Line Items]
Fair Value of Senior Notes	25,952
Series 2007A Tranche D [Member]
Fair Value Of Financial Instruments [Line Items]
Fair Value of Senior Notes	$40,777

Business_Segments_Additional_I

Business Segments - Additional Information (Detail)	12 Months Ended
	Mar. 31, 2015
	Plant
	Facility
	Segment
	Location
	Terminal
Segment Reporting Information [Line Items]
Number of operating business segments	5
Cement plant locations	6
Cement distribution terminals	16
Gypsum wallboard plants	5
Readymix concrete batch plant	17
Aggregates processing plant	4
Number of frac sand processing facilities	2
Number of frac sand drying facilities	3
Number of frac sand trans-load locations	4
Proportionate consolidation of share of Joint Venture's revenues and operating earnings	50.00%
Cement [Member]
Segment Reporting Information [Line Items]
Number of Joint Venture	1

Financial_Information_Related_

Financial Information Related to Operations by Segment (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Net Revenues	$223,780	$291,529	$284,808	$266,251	$189,894	$228,812	$252,646	$227,044	$1,066,368	$898,396	$642,562
Operating Earnings									302,301	224,638	134,520
Corporate General and Administrative Expense									-30,751	-24,552	-23,918
Acquisition, Litigation and Other Expense									-6,880		-10,683
Earnings Before Interest and Income Taxes									264,670	200,086	99,919
Interest Expense, Net									-11,743	-18,282	-15,823
Earnings before Income Taxes	44,698	77,866	74,577	55,786	29,767	48,833	58,688	44,516	252,927	181,804	84,096
Capital Expenditures									111,573	59,490	53,011
Depreciation, Depletion and Amortization									76,299	70,021	56,850
Identifiable Assets	1,882,591				1,511,529				1,882,591	1,511,529	1,476,233
Joint Venture [Member]
Segment Reporting Information [Line Items]
Net Revenues									-126,220	-111,393	-96,322
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									1,258,121	1,071,883	788,871
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net Revenues									65,533	62,094	49,987
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating Earnings									3,201	1,368	21
Capital Expenditures									135	249	10
Identifiable Assets	25,655				31,777				25,655	31,777	29,000
Cement [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									488,644	438,224	304,125
Cement Sales Volume									4,799	4,593	3,303
Operating Earnings									117,527	89,486	46,228
Capital Expenditures									27,086	12,226	15,583
Depreciation, Depletion and Amortization									31,839	31,829	20,658
Identifiable Assets	777,956				762,578				777,956	762,578	756,158
Cement [Member] | Operating Segments [Member] | Joint Venture [Member]
Segment Reporting Information [Line Items]
Cement Sales Volume									1,055	1,013	913
Operating Earnings									44,967	37,811	32,507
Cement [Member] | Operating Segments [Member] | Wholly-Owned [Member]
Segment Reporting Information [Line Items]
Cement Sales Volume									3,744	3,580	2,390
Operating Earnings									72,560	51,675	13,721
Cement [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net Revenues									9,598	8,952	2,850
Gypsum Wallboard [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									437,514	387,016	306,529
Operating Earnings									145,871	114,852	69,712
Capital Expenditures									7,129	4,825	2,682
Depreciation, Depletion and Amortization									20,092	20,981	21,045
Identifiable Assets	403,279				412,566				403,279	412,566	425,866
Paperboard [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									142,690	130,178	121,930
Operating Earnings									31,512	23,610	25,200
Capital Expenditures									1,888	3,354	804
Depreciation, Depletion and Amortization									8,251	8,716	8,824
Identifiable Assets	123,519				125,045				123,519	125,045	129,226
Paperboard [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net Revenues									55,060	52,119	46,393
Oil and Gas Proppants [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									81,381	19,557
Operating Earnings									-2,546	-4,890	-1,253
Capital Expenditures									61,484	34,264
Depreciation, Depletion and Amortization									8,839	1,707
Identifiable Assets	455,572				92,199				455,572	92,199	48,929
Concrete and Aggregates [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Revenues									107,892	96,908	56,287
Operating Earnings									6,736	212	-5,388
Capital Expenditures									13,851	4,572	33,932
Depreciation, Depletion and Amortization									5,533	5,205	5,212
Identifiable Assets	96,610				87,364				96,610	87,364	87,054
Concrete and Aggregates [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net Revenues									875	1,023	744
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Depreciation, Depletion and Amortization									$1,745	$1,583	$1,111

Segment_Breakdown_of_Goodwill_

Segment Breakdown of Goodwill (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Segment Reporting Information [Line Items]
Goodwill	$132,515	$132,515
Cement [Member]
Segment Reporting Information [Line Items]
Goodwill	8,359	8,359
Gypsum Wallboard [Member]
Segment Reporting Information [Line Items]
Goodwill	116,618	116,618
Paperboard [Member]
Segment Reporting Information [Line Items]
Goodwill	$7,538	$7,538

Schedule_of_Components_of_Prov

Schedule of Components of Provision for Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Current Provision (Benefit) - Federal	$62,424	$49,604	$19,108
Current Provision (Benefit) - State	-2,155	2,211	1,089
Current Provision (Benefit) - Total	60,269	51,815	20,197
Deferred Provision (Benefit) - Federal	-962	7,691	5,173
Deferred Provision (Benefit) - State	6,767	-1,945	982
Deferred Provision (Benefit) - Total	5,805	5,746	6,155
Provision for Income Taxes	$66,074	$57,561	$26,352

Schedule_of_Effective_Tax_Rate

Schedule of Effective Tax Rates Vary from Federal Statutory Rates (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Earnings Before Income Taxes	$44,698	$77,866	$74,577	$55,786	$29,767	$48,833	$58,688	$44,516	$252,927	$181,804	$84,096
Income Taxes at Statutory Rate									88,524	63,631	29,434
Increases (Decreases) in Tax Resulting from - State Income Taxes, net									4,582	173	1,346
Increases (Decreases) in Tax Resulting from - Statutory Depletion in Excess of Cost									-4,367	-3,512	-3,110
Increases (Decreases) in Tax Resulting from - Domestic Production Activities Deduction									-6,853	-3,453	-1,895
Increases (Decreases) in Tax Resulting from - Meals and Entertainment Disallowance									647	503	337
Increases (Decreases) in Tax Resulting from - Penalties on Uncertain Tax Positions										213	215
Increases (Decreases) in Tax Resulting from - IRS Settlement									-16,559
Increases (Decreases) in Tax Resulting from - Other									100	6	25
Provision for Income Taxes									$66,074	$57,561	$26,352
Effective Tax Rate									26.00%	32.00%	31.00%

Schedule_of_Deferred_Income_Ta

Schedule of Deferred Income Tax Provision (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	$5,805	$5,746	$6,155
Excess Tax Depreciation and Amortization [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	2,259	6,875	7,038
Bad Debts [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	-142	-224	-73
Uniform Capitalization [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	1,296	-1,127	-14
Accrual Changes [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	-611	-1,075	-1,169
Uncertain Tax Position Accruals [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision		213	173
Prepaid Insurance [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	-331	424
State Income Taxes, net [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	6,060	-1,319	1,130
Long-Term Incentive Compensation Plans [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	-1,792	-373	1,293
Other [Member]
Deferred Income Benefit Taxes [Line Items]
Deferred Income Tax Provision	($934)	$1,033	($1,093)

Schedule_of_Components_of_Defe

Schedule of Components of Deferred Income Taxes (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]
Items Giving Rise to Deferred Tax Liabilities - Excess Tax Depreciation and Amortization	($153,045)	($144,519)
Items Giving Rise to Deferred Tax Liabilities - Depletion	-18,374	-100
Items Giving Rise to Deferred Tax Liabilities - Repair Parts	-3,376	-4,545
Items Giving Rise to Deferred Tax Liabilities - State Income Taxes, net	-13,708	-7,648
Items Giving Rise to Deferred Tax Liabilities - Other	-5,359	-9,125
Items Giving Rise to Deferred Tax Liabilities - Total Deferred Tax Liabilities	-193,862	-165,937
Items Giving Rise to Deferred Tax Assets - Accrual Changes	10,557	9,946
Items Giving Rise to Deferred Tax Assets - Bad Debts	2,264	2,122
Items Giving Rise to Deferred Tax Assets - Uniform Capitalization	835	2,131
Items Giving Rise to Deferred Tax Assets - Deferred Revenue	4,382
Items Giving Rise to Deferred Tax Assets - Long-term Incentive Compensation Plan	8,318	6,526
Items Giving Rise to Deferred Tax Assets - Other	7,118
Items Giving Rise to Deferred Tax Assets - Total Deferred Tax Assets	$33,474	$20,725

Schedule_of_Income_Taxes_Class

Schedule of Income Taxes Classified in Consolidated Balance Sheet (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]
Prepaid and Other Assets	$2,265	$561
Deferred Income Taxes	($162,653)	($145,773)

Reconciliation_of_Consolidated

Reconciliation of Consolidated Liability for Gross Unrecognized Tax Benefits (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Balance at Beginning of Year	$24,802	$24,589	$25,890
Increase related to prior tax positions		213	215
Decrease related to prior tax positions	-24,802		-1,516
Balance at End of Year		$24,802	$24,589

Summary_of_Amounts_of_Interest

Summary of Amounts of Interest and Penalties Recognized in Relation to Uncertain Tax Position (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Accrued interest recognized	($3,847)	$641	$409
Accrued penalties recognized	($6,475)	$213	$173

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Accrued interest on uncertain tax position	$0	$0	$4.40
Accrued penalities on uncertain tax position	0	0	3.2
Percentage of penalties and related interest assessed to date	40.00%
Impact from settlement agreement	17	17
Interest related to tax penalties	$4.40	$4.40

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
	GeneratingPlant
Product Liability Contingency [Line Items]
Letters of credit outstanding, amount	$9,200,000
Contingently liable for performance, current	14,800,000
Outstanding guarantees	0
Sale percentage of gypsum-grade recycled paperboard	90.00%
Number of plants	3
Percentage of expected natural gas usage	25.00%
Operating leases Rental expense	$5,900,000	$3,200,000	$1,600,000
Minimum [Member]
Product Liability Contingency [Line Items]
Sale percentage of gypsum-grade recycled paperboard	15.00%
Maximum [Member]
Product Liability Contingency [Line Items]
Sale percentage of gypsum-grade recycled paperboard	20.00%

Schedule_of_Minimum_Annual_Ren

Schedule of Minimum Annual Rental Commitments (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]
2016	$11,043
2017	9,834
2018	7,610
2019	6,544
2020	4,171
Thereafter	$13,758

Stock_Option_Plans_Additional_

Stock Option Plans - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended
	Jun. 30, 2014	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Aug. 31, 2014	Aug. 07, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant		4,907,503				3,000,000
Period of average return on invested capital exceeded target	10 years
Stock option expense		$6,200,000	$5,300,000	$4,000,000
Aggregate intrinsic value for outstanding options		61,900,000
Aggregate intrinsic value of exercisable options		50,800,000
Total intrinsic value of options exercised		9,600,000
Restricted stock or unit expense		6,700,000	4,800,000	3,400,000
Maximum number of shares available for grant		1,491,297
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant						1,500,000
Unrecognized compensation cost, stock options		11,400,000
Weighted-average period of recognition of unrecognized compensation cost		3 years 3 months 18 days
Fiscal 2015 Employee Stock Option Grant [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted	193,636
Period of average return on invested capital exceeded target	10 years
Share-based compensation vesting period		3 years
Share-based compensation award expiration term		10 years
Fiscal 2015 Employee Stock Option Grant [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital		15.00%
Share-based compensation vesting date		31-Mar-16
Fiscal 2015 Employee Stock Option Grant [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation vesting date		31-Mar-17
Fiscal 2015 Board of Directors Grant [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Granted					18,515
Share-based compensation award expiration term		10 years
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, stock options		100,000
Weighted-average period of recognition of unrecognized compensation cost		1 year
Restricted stock or unit expense		0	0	1,600,000
Unvested RSUs (in shares)		20,000
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant	80,416				7,457
Weighted-average period of recognition of unrecognized compensation cost		2 years 6 months
Remaining restrictions of unearned compensation cost		500,000
Unrecognized compensation cost		$17,000,000
Restricted Stock [Member] | Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation vesting period		5 years
Restricted Stock [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of average return on invested capital		15.00%
Share-based compensation vesting date		31-Mar-16
Restricted Stock [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation vesting date		31-Mar-19

WeightedAverage_Assumptions_Us

Weighted-Average Assumptions Used to Value Option Awards (Detail) (Fiscal 2015 Employee Stock Option and Board of Directors Grant [Member])	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Fiscal 2015 Employee Stock Option and Board of Directors Grant [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend Yield	2.00%	2.00%
Expected Volatility	44.80%	44.60%
Risk Free Interest Rate	1.86%	2.04%
Expected Life	6 years	7 years

Stock_Option_Activity_Detail

Stock Option Activity (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Options at Beginning of Year	2,788,999	3,022,592	3,241,322
Number of Shares, Granted	297,151	256,989	569,679
Number of Shares, Exercised	-151,085	-485,582	-746,131
Number of Shares, Cancelled	-1,269,500	-5,000	-42,278
Number of Shares, Outstanding Options at End of Year	1,665,565	2,788,999	3,022,592
Number of Shares, Options Exercisable at End of Year	1,035,166	818,215	986,187
Weighted-Average Exercise Price, Outstanding Options at Beginning of year	$41.83	$37.83	$36.11
Weighted-Average Exercise Price, Granted	$86.41	$68	$34.64
Weighted-Average Exercise Price, Exercised	$32.38	$29.72	$27.64
Weighted-Average Exercise Price, Cancelled	$47.43	$53.22	$42.21
Weighted-Average Exercise Price, Outstanding Options at End of Year	$46.37	$41.83	$37.83
Weighted-Average Exercise Price, Weighted-Average Fair Value of Options Granted during the Year	$32.31	$26.35	$13.28

Stock_Options_Outstanding_Deta

Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number of Shares Outstanding	1,665,565
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 6 months 15 days
Options Outstanding, Weighted-Average Exercise Price	$46.37
Options Exercisable, Number of Shares Outstanding	1,035,166
Options Exercisable, Weighted-Average Exercise Price	$34.52
$23.17 - $30.74 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$23.17
Range of Exercise Prices, Upper Range	$30.74
Options Outstanding, Number of Shares Outstanding	592,210
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 2 months 9 days
Options Outstanding, Weighted-Average Exercise Price	$26.50
Options Exercisable, Number of Shares Outstanding	589,210
Options Exercisable, Weighted-Average Exercise Price	$26.48
$33.08 - $40.78 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$33.08
Range of Exercise Prices, Upper Range	$40.78
Options Outstanding, Number of Shares Outstanding	487,968
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 10 months 28 days
Options Outstanding, Weighted-Average Exercise Price	$33.95
Options Exercisable, Number of Shares Outstanding	308,352
Options Exercisable, Weighted-Average Exercise Price	$34
$53.22 – $ 74.10 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$53.22
Range of Exercise Prices, Upper Range	$74.10
Options Outstanding, Number of Shares Outstanding	283,236
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 9 months 26 days
Options Outstanding, Weighted-Average Exercise Price	$66.58
Options Exercisable, Number of Shares Outstanding	118,089
Options Exercisable, Weighted-Average Exercise Price	$66.59
$79.90 - $ 93.56 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$79.90
Range of Exercise Prices, Upper Range	$93.56
Options Outstanding, Number of Shares Outstanding	302,151
Options Outstanding, Weighted-Average Remaining Contractual Life	9 years 3 months 22 days
Options Outstanding, Weighted-Average Exercise Price	$86.42
Options Exercisable, Number of Shares Outstanding	19,515
Options Exercisable, Weighted-Average Exercise Price	$91.71

Interest_Expense_Net_Detail

Interest Expense, Net (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Interest Income (Expense), Net [Abstract]
Interest Income	($6)	($5)	($53)
Interest Expense	14,768	16,751	14,769
Interest Expense (Income) – IRS	-3,847	641	409
Other Expenses	828	895	698
Interest Expense, net	$11,743	$18,282	$15,823

Net_Interest_Expense_Additiona

Net Interest Expense - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2015
Interest Expense [Abstract]
Interest related to tax penalties	$4.40	$4.40

Schedule_of_Reconciliation_of_

Schedule of Reconciliation of Obligations and Fair Values of Plan Assets (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Compensation And Retirement Disclosure [Abstract]
Benefit Obligation at April 1,	$29,892	$29,586
Service Cost - Benefits Earned During the Period	874	1,129	785
Interest Cost on Projected Benefit Obligation	1,278	1,222	1,222
Amendments	805
Actuarial (Gain) Loss	9,823	-1,237
Benefits Paid	-881	-808
Benefit Obligation at March 31,	41,791	29,892	29,586
Fair Value of Plan Assets at April 1,	21,189	18,693
Actual Return on Plan Assets	937	1,735
Employer Contributions	810	1,569
Fair Value of Plans at March 31,	22,055	21,189	18,693
Unfunded Status at March 31,	-19,736	-8,703
Accrued Benefit Liability	-19,736	-8,703
Accumulated Other Comprehensive Losses - Net Actuarial Loss	18,376	8,419
Accumulated Other Comprehensive Losses - Prior Service Cost	809	15
Accumulated Other Comprehensive Losses	19,185	8,434
Tax impact	-7,118	-2,952
Accumulated Other Comprehensive Losses, net of tax	$12,067	$5,482

Schedule_of_Accumulated_Benefi

Schedule of Accumulated Benefit Obligation in Excess of Plan Assets (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified
Compensation And Retirement Disclosure [Abstract]
Projected Benefit Obligation	$41,791	$29,892	$29,586
Accumulated Benefit Obligation	41,790	29,827
Fair Value of Plan Assets	$22,055	$21,189	$18,693

Components_of_Net_Periodic_Cos

Components of Net Periodic Cost (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Compensation And Retirement Disclosure [Abstract]
Service Cost - Benefits Earned During the Period	$874	$1,129	$785
Interest Cost of Projected Benefit Obligation	1,278	1,222	1,222
Expected Return on Plan Assets	-1,680	-1,506	-1,371
Recognized Net Actuarial Loss	609	921	980
Amortization of Prior-Service Cost	11	11	21
Net Periodic Pension Cost	$1,092	$1,777	$1,637

Pension_and_Profit_Sharing_Pla2

Pension and Profit Sharing Plans - Additional information (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2016
	CompensationPlan
	Employee
Defined Benefit Plan Disclosure [Line Items]
Amendment of pension plan service cost	$805,000
Amendment in pension plan	We amended one of our pension plans during March 2015, which increased our prior service cost by approximately $0.8 million. This amount is included in other comprehensive income and will be recognized in our statement of earnings as pension expense over the next three fiscal years.
Current actuarial estimates contributions	200,000	200,000	100,000
Costs relating to employer discretionary contributions	5,300,000	4,500,000	3,300,000
Number of employees covered under multi-employer pension plans	60
Number of multi-employer plans	5
Collective bargaining agreement for employer covered under multi-employer plans, Expiration beginning date	30-Jun-15
Collective bargaining agreement for employer covered under multi-employer plans, Expiration ending date	31-Mar-17
Expenses related to Multi employer plans	1,000,000	1,000,000	200,000
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Expenses related to Multi employer plans				1,000,000
Salaried Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Employees fully vesting in employer's contributions made beginning in 2007, requirement years	6 years
Hourly Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Employees fully vesting in employer's contributions made beginning in 2007, requirement years	3 years
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Current actuarial estimates contributions	500,000
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Current actuarial estimates contributions	$1,000,000

Schedule_of_Expected_Benefit_P

Schedule of Expected Benefit Payments (Detail) (USD $)	Mar. 31, 2015
In Thousands, unless otherwise specified
Compensation And Retirement Disclosure [Abstract]
2016	$1,115
2017	1,167
2018	1,219
2019	1,302
2020	1,389
2021-2025	$8,908

Schedule_of_Assumptions_Used_i

Schedule of Assumptions Used in Net Periodic Benefit Cost and Benefit Obligations (Detail)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Compensation And Retirement Disclosure [Abstract]
Net Periodic Benefit Costs - Discount Rate	4.41%	4.20%	4.56%
Net Periodic Benefit Costs - Expected Return on Plan Assets	8.00%	8.00%	8.00%
Net Periodic Benefit Costs - Rate of Compensation Increase	3.50%	3.50%	3.50%
Benefit Obligations - Discount Rate	3.70%	4.41%
Benefit Obligations - Rate of Compensation Increase	3.50%	3.50%

Schedule_of_Pension_Plans_Weig

Schedule of Pension Plans Weighted-Average Asset Allocation and Range of Target Allocation (Detail)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets at March 31	100.00%	100.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Range of Target Allocation - Minimum	40.00%
Range of Target Allocation - Maximum	60.00%
Percentage of Plan Assets at March 31	61.00%	65.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Range of Target Allocation - Minimum	35.00%
Range of Target Allocation - Maximum	60.00%
Percentage of Plan Assets at March 31	36.00%	30.00%
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Range of Target Allocation - Minimum	0.00%
Range of Target Allocation - Maximum	5.00%
Percentage of Plan Assets at March 31	3.00%	5.00%

Schedule_of_Fair_Values_of_Def

Schedule of Fair Values of Defined Benefit Plans (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$22,055	$21,189	$18,693
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	13,510	13,973
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	7,985	6,526
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	133	130
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Commodity Linked Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$124	$170

Schedule_of_Fair_Values_of_Def1

Schedule of Fair Values of Defined Benefit Plans Determined Using Fair Value Hierarchy of Inputs (Detail) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$22,055	$21,189	$18,693
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	13,510	13,973
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	7,985	6,526
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	133	130
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Commodity Linked Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	124	170
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Fair Value, Inputs, Level 1 | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	303	390
Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	21,752	20,799
Fair Value, Inputs, Level 2 | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	13,510	13,973
Fair Value, Inputs, Level 2 | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	7,985	6,526
Fair Value, Inputs, Level 2 | Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	133	130
Fair Value, Inputs, Level 2 | Commodity Linked Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plans	$124	$170

Quarterly_Results_unaudited_De

Quarterly Results (unaudited) (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenues	$223,780	$291,529	$284,808	$266,251	$189,894	$228,812	$252,646	$227,044	$1,066,368	$898,396	$642,562
Gross Profit	43,522	79,149	75,061	56,401	29,528	49,848	59,479	46,604	254,133	185,459	103,245
Earnings Before Income Taxes	44,698	77,866	74,577	55,786	29,767	48,833	58,688	44,516	252,927	181,804	84,096
Net Earnings	$46,794	$52,030	$50,319	$37,710	$22,618	$31,621	$39,903	$30,101	$186,853	$124,243	$57,744
Diluted Earnings Per Share	$0.93	$1.03	$1	$0.75	$0.45	$0.63	$0.80	$0.60	$3.71	$2.49	$1.22

Quarterly_Results_unaudited_Ad

Quarterly Results (unaudited) - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Impact from settlement agreement	$17		$17
Interest related to tax penalties	4.4		4.4
Business acquisition and litigation expenses	4.1
Maintenance and repair expenses		4.5	86.7	77.4	61.3
Legal costs		1.3
Maintenance costs		1.5
Cost of natural gas		$0.90