Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Mar. 31, 2014
Statement of Financial Position [Abstract]
Property and equipment, accumulated depreciation	$ 816,317	$ 805,687
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized shares	10,000,000us-gaap_PreferredStockSharesAuthorized	10,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, issued shares	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	175,000,000us-gaap_CommonStockSharesAuthorized	175,000,000us-gaap_CommonStockSharesAuthorized
Common stock, issued shares	46,508,000us-gaap_CommonStockSharesIssued	46,508,000us-gaap_CommonStockSharesIssued
Treasury stock, shares	1,384,000us-gaap_TreasuryStockShares	1,519,000us-gaap_TreasuryStockShares

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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