Borrowings - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Schedule of Borrowings [Line Items]
Unutilized borrowing facilities	¥ 27,458	¥ 15,000
Subordinated borrowings	¥ 657,463	¥ 489,888
Fixed-rate obligations [Member]
Schedule of Borrowings [Line Items]
Long-term borrowings, Maturities start period	2016	2015
Long-term borrowings, Maturities end period	2046	2045
Long-term borrowings, Minimum interest rate	0.00%	0.00%
Long-term borrowings, Maximum interest rate	14.53%	12.66%
Floating-rate obligations [Member]
Schedule of Borrowings [Line Items]
Long-term borrowings, Maturities start period	2016	2015
Long-term borrowings, Maturities end period	2047	2052
Long-term borrowings, Minimum interest rate	0.00%	0.00%
Long-term borrowings, Maximum interest rate	9.01%	9.02%
Index / Equity-linked obligations [Member]
Schedule of Borrowings [Line Items]
Long-term borrowings, Maturities start period	2016	2015
Long-term borrowings, Maturities end period	2046	2045
Long-term borrowings, Minimum interest rate	0.00%	0.00%
Long-term borrowings, Maximum interest rate	31.00%	28.50%

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Debt Instruments Maturity Date Range Start

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Schedule Of Borrowings

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Amount of unutilized borrowing facilities under financing arrangement that is available to the entity as of the balance sheet date.

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- Definition

When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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When presenting a range of interest rates, the lowest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: 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

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Article 5
-Subsection 19, 20, 22

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 10
-Section F

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