Commitments and Contingencies (Litigation and Other Proceedings) - Additional Information (Detail) $ in Millions	6 Months Ended
Sep. 30, 2018 USD ($)
Federal Securities Laws Violation [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Payment of penalties for legal fees and expenses	$ 1.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration