Reconciliation of Differences between Tax Provision Computed and Consolidated Provisions for Income Taxes (Detail) In Millions	12 Months Ended
Mar. 31, 2011 USD ($)	Mar. 31, 2011 JPY (¥)	Mar. 31, 2010 JPY (¥)	Mar. 31, 2009 JPY (¥)
Reconciliation of Provision of Income Taxes [Line Items]
Income before income taxes and discontinued operations	$ 1,106	¥ 91,965	¥ 54,593	¥ 12,035
Tax provision computed at statutory rate	452	37,614	22,329	4,922
Increases (reductions) in taxes due to:
Change in valuation allowance	(47)	(3,944)	1,859	5,678
Non-deductible expenses for tax purposes	13	1,123	1,640	1,755
Non-taxable income for tax purposes	(32)	(2,697)	(779)	(976)
Effect of lower tax rates on foreign subsidiaries and a domestic life insurance subsidiary	(52)	(4,335)	(3,699)	(1,479)
Effect of a revision of the taxation system	0	0	0	(10,970)
Other, net	(2)	(144)	1,044	(1,528)
Provision for income taxes	$ 332	¥ 27,617	¥ 22,394	¥ (2,598)

Income from continuing operations before income taxes and noncontrolling interest

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Income Tax Reconciliation Effect Of Revision Of Taxation System

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Income Tax Reconciliation Increases Decreases [Abstract]

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Income Tax Reconciliation, Rate Adjustment

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Reconciliation of Provision of Income Taxes [Line Items]

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The sum of the current income tax expense (benefit) and the deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 45
-Subparagraph a, b

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The portion of the difference between total income tax expense (benefit) as reported in the Income Statement and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 26

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The sum of the differences between total income tax expense (benefit) as reported in the Income Statement for the period and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to all deductions taken under enacted tax laws which were not recognized as expense under generally accepted accounting principles.

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The amount of income tax expense (benefit) for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 47

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Subparagraph 2
-Article 4

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The sum of the differences between total income tax expense (benefit) as reported in the Income Statement for the period and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to nondeductible expenses under enacted tax laws, or differences in the methodologies used to determine expense amounts for financial statements prepared in accordance with generally accepted accounting principles and enacted tax laws.

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The portion of the difference, between total income tax expense (benefit) as reported in the Income Statement for the year/accounting period and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to all other items not otherwise listed in the existing taxonomy.

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