Components of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net Income available to common shareholders (A)	$ (160,694)us-gaap_NetIncomeLoss	$ 12,583us-gaap_NetIncomeLoss	$ (56,114)us-gaap_NetIncomeLoss	$ 96,838us-gaap_NetIncomeLoss
Weighted average outstanding shares of common stock, basic (B)	48,481,722	49,347,448	49,213,712	49,302,971
Dilutive effect of options and restricted stock awards and units		482,818		436,758
Weighted average common stock and equivalents (C)	48,481,722	49,830,266	49,213,712	49,739,729
Earnings per share, basic (A/B)	$ (3.31)us-gaap_EarningsPerShareBasic	$ 0.25us-gaap_EarningsPerShareBasic	$ (1.14)us-gaap_EarningsPerShareBasic	$ 1.96us-gaap_EarningsPerShareBasic
Earnings per share, diluted (A/C)	$ (3.31)us-gaap_EarningsPerShareDiluted	$ 0.25us-gaap_EarningsPerShareDiluted	$ (1.14)us-gaap_EarningsPerShareDiluted	$ 1.95us-gaap_EarningsPerShareDiluted
Antidilutive incremental options and restricted stock awards and units	158,575		231,171

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