Reconciliation of the Differences between Basic and Diluted EPS - Additional Information (Detail) - shares shares in Thousands	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Potential shares of common stock upon the exercise of stock acquisition rights and convertible bonds excluded from the computation of diluted EPS	2,921	6,856	11,357

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration