Income Taxes - Reconciliation of Unrecognized Tax Benefits and Interest and Penalties (Detail) - USD ($)	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, Beginning balance	$ 700,000	$ 700,000	$ 4,900,000
Unrecognized tax benefits, Additions for tax positions of the current year	0	100,000	200,000
Unrecognized tax benefits, Reductions in tax positions of prior year	0	(100,000)	(4,100,000)
Unrecognized tax benefits, Settlements paid during the current period			(300,000)
Unrecognized tax benefits, Ending Balance	700,000	700,000	700,000
Interest and Penalties, Beginning balance	0	0	300,000
Interest And Penalties, Reductions in tax position of prior year			(300,000)
Interest and Penalties, Ending Balance	$ 0	$ 0	$ 0

Interest and penalties additions deletions for tax positions of prior year.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

+ Details

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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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- Definition

Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319

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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

+ References

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