Changes in Components of Accumulated Other Comprehensive Income (Loss) (Detail) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2012 USD ($)	Mar. 31, 2012 JPY (¥)	Mar. 31, 2011 JPY (¥)	Mar. 31, 2010 JPY (¥)	Mar. 31, 2012 Accumulated Net Unrealized Investment Gain (Loss) USD ($)	Mar. 31, 2012 Accumulated Net Unrealized Investment Gain (Loss) JPY (¥)	Mar. 31, 2011 Accumulated Net Unrealized Investment Gain (Loss) JPY (¥)	Mar. 31, 2010 Accumulated Net Unrealized Investment Gain (Loss) JPY (¥)	Mar. 31, 2012 Accumulated Defined Benefit Plans Adjustment USD ($)	Mar. 31, 2012 Accumulated Defined Benefit Plans Adjustment JPY (¥)	Mar. 31, 2011 Accumulated Defined Benefit Plans Adjustment JPY (¥)	Mar. 31, 2010 Accumulated Defined Benefit Plans Adjustment JPY (¥)	Mar. 31, 2012 Accumulated Translation Adjustment USD ($)	Mar. 31, 2012 Accumulated Translation Adjustment JPY (¥)	Mar. 31, 2011 Accumulated Translation Adjustment JPY (¥)	Mar. 31, 2010 Accumulated Translation Adjustment JPY (¥)	Mar. 31, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges USD ($)	Mar. 31, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges JPY (¥)	Mar. 31, 2011 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges JPY (¥)	Mar. 31, 2010 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges JPY (¥)
Beginning Balance	$ (1,170)	¥ (96,180)	¥ (79,459)	¥ (92,384)	$ 140	¥ 11,503	¥ 7,495	¥ (5,615)	$ (135)	¥ (11,098)	¥ (9,092)	¥ (16,221)	$ (1,163)	¥ (95,574)	¥ (77,651)	¥ (71,791)	$ (12)	¥ (1,011)	¥ (211)	¥ 1,243
Cumulative effect of applying new accounting standards for the consolidation of variable interest entities, net of tax of ¥2,265 million			(3,406)				(3,597)								191
Beginning Balance Restated			(82,865)				3,898				(9,092)				(77,460)				(211)
Net unrealized gains on investment in securities, net of tax of ¥(2,820) million or $(34) million in 2012, ¥(2,379) million in 2011 and ¥(6,610) million in 2010	84	6,963	3,292	11,357	84	6,963	3,292	11,357
Reclassification adjustment included in net income, net of tax of ¥1,463 million or $17 million in 2012, ¥(3,289) million in 2011, and ¥(1,206) million in 2010	(28)	(2,321)	4,313	1,753	(28)	(2,321)	4,313	1,753
Defined benefit pension plans, net of tax of ¥1,807 million or $22 million in 2012, ¥1,339 million in 2011, and ¥(4,567) million in 2010	(40)	(3,292)	(1,934)	6,601					(40)	(3,292)	(1,934)	6,601
Reclassification adjustment included in net income, net of tax of ¥(33) million or $0 million in 2012, ¥ 88 million in 2011, and ¥ (358) million in 2010	0	47	(72)	528					0	47	(72)	528
Foreign currency translation adjustments, net of tax of ¥(335) million or $(4) million 2012, ¥ 245 million in 2011, and ¥(4,487) million in 2010	(1)	(118)	(18,158)	(6,199)									(1)	(118)	(18,158)	(6,199)
Reclassification adjustment included in net income, net of tax of ¥ 0 million or $0 million in 2012, (31) million in 2011, and ¥ (235) million in 2010	0	0	44	339									0	0	44	339
Net unrealized gains (losses) on derivative instruments, net of tax of ¥450 million or $6 million in 2012, ¥488 million in 2011, and ¥743 million in 2010	(12)	(974)	(1,011)	(630)													(12)	(974)	(1,011)	(630)
Reclassification adjustment included in net income, net of tax of ¥198 million or $2 million in 2012, ¥(150) million in 2011, and ¥323 million in 2010	(2)	(181)	211	(824)													(2)	(181)	211	(824)
Change during year	1	124	(13,315)	12,925	56	4,642	7,605	13,110	(40)	(3,245)	(2,006)	7,129	(1)	(118)	(18,114)	(5,860)	(14)	(1,155)	(800)	(1,454)
Ending Balance	$ (1,169)	¥ (96,056)	¥ (96,180)	¥ (79,459)	$ 196	¥ 16,145	¥ 11,503	¥ 7,495	$ (175)	¥ (14,343)	¥ (11,098)	¥ (9,092)	$ (1,164)	¥ (95,692)	¥ (95,574)	¥ (77,651)	$ (26)	¥ (2,166)	¥ (1,011)	¥ (211)

Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Restated

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Other Comprehensive Income, Defined Benefit Plans Net Unamortized (Gain) Loss Arising During Period, Net of Tax, Attributable to Parent

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Other Comprehensive Income, Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax, Attributable to Parent

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Other Comprehensive Income, Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, Net of Tax, Attributable to Parent

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Other Comprehensive Income, Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax, Attributable to Parent

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Other Comprehensive Income, Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax, Attributable to Parent

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Other Comprehensive Income, Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax, Attributable to Parent

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Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax, attributable to the parent entity. Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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The after tax effect on other comprehensive income of a change in accounting principle recognized in the period, which occurred before retrospective adjustments were required, or is in lieu of retrospective adjustments.

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This element represents Other Comprehensive Income or Loss, Net of Tax, for the period attributable to the parent entity. Includes deferred gains or losses on qualifying hedges, unrealized holding gains or losses on available-for-sale securities, minimum pension liability, and cumulative translation adjustment.

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