Investment in Operating Leases (Depreciation and Various Expenses Included in Costs of Operating Leases) (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Leases [Abstract]
Depreciation expenses	¥ 209,586	¥ 202,858	¥ 195,047
Various expenses	80,018	54,463	57,280
Costs of operating leases	¥ 289,604	¥ 257,321	¥ 252,327

The total various expenses (insurance, property tax and other) recorded for property subject to or held for lease.

No definition available.

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Namespace Prefix:	ck0001070304_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense incurred and directly related to generating revenue from leased and rented property or equipment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(c))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

The total depreciation charge recorded for property subject to or held for lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration