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

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.