Schedule of Deferred Income Tax Provision (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	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)