Life Insurance Premiums and Related Investment Income (Detail) In Millions	12 Months Ended
Mar. 31, 2011 USD ($)	Mar. 31, 2011 JPY (¥)	Mar. 31, 2010 JPY (¥)	Mar. 31, 2009 JPY (¥)
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Life insurance premiums	$ 1,297	¥ 107,860	¥ 104,133	¥ 115,214
Life insurance related investment income	128	10,613	11,465	2,537
Life insurance premiums and related investment income	$ 1,425	¥ 118,473	¥ 115,598	¥ 117,751

Revenues from Premiums earned on the income statement for all insurance and reinsurance contracts after subtracting any amounts ceded to another insurer and adding premiums assumed from other insurers and revenues from insurance-related investments.

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- Definition

Investment income associated with the company's insurance services.

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- Definition

Premiums recognized as revenue in the period earned on all life insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 113
-Paragraph 27

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 17
-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 1
-Article 7

+ Details

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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.

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