Other Intangible Assets Recognized in the Acquisition (Detail) (Robeco Groep N. V., JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2014
Business Acquisition [Line Items]
Acquired intangible assets not subject to amortization recorded at fair value	¥ 170,795
Acquired Intangibles subject to amortization recorded at fair value	34,935
Total	205,730
Asset management contracts
Business Acquisition [Line Items]
Acquired intangible assets not subject to amortization recorded at fair value	152,680
Trade names
Business Acquisition [Line Items]
Acquired intangible assets not subject to amortization recorded at fair value	18,115
Customer relationships
Business Acquisition [Line Items]
Acquired Intangibles subject to amortization recorded at fair value	32,994
Weighted average amortization period	7 years
Software
Business Acquisition [Line Items]
Acquired Intangibles subject to amortization recorded at fair value	¥ 1,941
Weighted average amortization period	7 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16265-109275

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- Definition

Amount of assets, excluding financial assets and goodwill, that lack physical substance, having a projected indefinite period of benefit, acquired at the acquisition date.

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- Definition

Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 55

-Paragraph 37

-URI http://asc.fasb.org/extlink&oid=25498275&loc=d3e2207-128464

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