Marketable Securities and Securities Investments - Additional Information (Detail) (JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Investment Holdings [Line Items]
Proceeds from sales of available-for-sale securities	¥ 177,850	¥ 532,619	¥ 785,698
Gross realized gains from available for sale securities	9,593	38,654	39,622
Gross realized loss from available for sale securities	1,834	2,014	37,537
Marketable securities classified as trading securities	433,491	375,802
Investment in non public companies	93,050	75,930
Net unrealized gains on trading securities	21,216		50,992
Net unrealized losses on trading securities		10,768
Total realized impairment losses on marketable securities	¥ 5,530	¥ 9,763	¥ 5,508

The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time, usually less than one year or the normal operating cycle, whichever is longer) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

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The increase (decrease) resulting in a gain from the difference between the fair value and the carrying value, or in the comparative fair values, of trading securities held at each balance sheet date, that was included in earnings for the period.

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