Securitizations and Variable Interest Entities - Type and Carrying Value of Financial Assets (Detail) - JPY (¥) ¥ in Millions	Mar. 31, 2016	Mar. 31, 2015
Liabilities [Abstract]
Long-term borrowings	¥ 8,129,559	¥ 8,336,296
Transferred to SPEs [Member]
Trading assets
Equities	22,000	83,000
Debt securities	24,000	26,000
CMBS and RMBS	¥ 20,000	¥ 22,000
Long-term loans receivable
Total	¥ 66,000	¥ 131,000
Liabilities [Abstract]
Long-term borrowings	¥ 127,000	¥ 129,000

Trading Assets And Liabilities Textual [Abstract]

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Trading Assets and Long-term Loans Receivable

+ References

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 20, 22
-Article 5

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- Definition

Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Mortgage-Backed Securities
-URI http://asc.fasb.org/extlink&oid=6517959

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The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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-Subparagraph (b)(1)(i)
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- Definition

Amount of investments in debt securities classified as trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6526789

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Fair value of investments in trading equity securities and other forms of trading securities that provide ownership interests.

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-Name Accounting Standards Codification
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