Investment in Direct Financing Leases - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Finance Revenues
Lease Disclosure [Line Items]
Direct financing leases revenues	¥ 58,246	¥ 59,900

Revenue realized in the period on direct financing leases.

No definition available.

Name:	us-gaap_CapitalLeasesIncomeStatementDirectFinancingLeaseRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration