Impacts of 10% and 20% Adverse Changes to Assumptions on Fair Value (Detail) (JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2010 Year
Direct financing leases
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests that continue to be held	¥ 76,136
Book value of the interests that continue to be held	67,028
Minimum weighted average life (in years)	2.0
Maximum weighted average life (in years)	3.4
Expected credit loss +10%	376
Expected credit loss +20%	756
Discount rate +10%	605
Discount rate +20%	1,198
Prepayment rate +10%	57
Prepayment rate +20%	117
Installment Commercial Mortgage Loans
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests that continue to be held	2,830
Book value of the interests that continue to be held	2,859
Weighted average life (in years)	0.7
Expected credit loss +10%	35
Expected credit loss +20%	70
Discount rate +10%	6
Discount rate +20%	12
Prepayment rate +10%	16
Prepayment rate +20%	32
Installment Mortgage Loans for individuals
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests that continue to be held	25,930
Book value of the interests that continue to be held	22,568
Minimum weighted average life (in years)	13.9
Maximum weighted average life (in years)	24.5
Expected credit loss +10%	47
Expected credit loss +20%	94
Discount rate +10%	402
Discount rate +20%	793
Prepayment rate +10%	173
Prepayment rate +20%	341
Investment in securities
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests that continue to be held	23,258
Book value of the interests that continue to be held	23,601
Minimum weighted average life (in years)	0.6
Maximum weighted average life (in years)	4.2
Expected credit loss +10%	50
Expected credit loss +20%	143
Discount rate +10%	311
Discount rate +20%	608
Prepayment rate +10%	2
Prepayment rate +20%	¥ 4

Assumption For Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Weighted Average Life Lower Limit

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- Definition

Assumption For Fair Value Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Weighted Average Life Upper Limit

+ Details

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- Definition

Interests Continued to be Held by Transferor, Book Value

+ Details

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

- Definition

The weighted average life of securitized assets. This is used as a key input and assumption in measuring the fair value of assets or liabilities that relate to a transferor's continuing involvement (including interests that continue to be held by the transferor and servicing assets or servicing liabilities), if any, as of the date of the latest statement of financial position presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(3)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(2)

+ Details

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- Definition

The carrying amount (fair value) as of the balance sheet date of interests in financial instruments (typically securitized receivables) that continue to be held (which are generally not involved in the collection of principal) following transfer of significant portions of such financial instruments to other parties. Such interests could be ancillary cash flows and interest-only strips.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i

+ Details

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- Definition

The hypothetical financial impact of a 10 percent adverse change of the discount rate on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 10 percent adverse change of the expected credit losses on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

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Period Type:	instant

- Definition

The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

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Namespace Prefix:	us-gaap
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Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 20 percent adverse change of the discount rate on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

Name:	us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf20PercentAdverseChangeInDiscountRate
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 20 percent adverse change of the expected credit losses on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of interests that continue to be held by the transferor, servicing assets, or servicing liabilities as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4 and FIN46(R)-8
-Paragraph B11
-Subparagraph b(5)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph i(3)

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ Details

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