Income Taxes - Summary of Income Tax Provision (Detail) (USD $)	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Current - Federal	$ 16,534,000us-gaap_CurrentFederalTaxExpenseBenefit	$ 21,978,000us-gaap_CurrentFederalTaxExpenseBenefit	$ 11,236,000us-gaap_CurrentFederalTaxExpenseBenefit
Current - State	136,000	2,656,000	3,653,000
Subtotal	16,670,000us-gaap_CurrentIncomeTaxExpenseBenefit	24,634,000us-gaap_CurrentIncomeTaxExpenseBenefit	14,889,000us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred - Federal	312,000	(2,367,000)	2,310,000
Deferred - State	(8,000)	(152,000)	(34,000)
Subtotal	304,000us-gaap_DeferredIncomeTaxExpenseBenefit	(2,519,000)us-gaap_DeferredIncomeTaxExpenseBenefit	2,276,000us-gaap_DeferredIncomeTaxExpenseBenefit
Total	$ 16,974,000us-gaap_IncomeTaxExpenseBenefit	$ 22,115,000us-gaap_IncomeTaxExpenseBenefit	$ 17,165,000us-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.