Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Detail) In Millions	12 Months Ended
Mar. 31, 2011 USD ($)	Mar. 31, 2011 JPY (¥)	Mar. 31, 2010 JPY (¥)	Mar. 31, 2009 JPY (¥)
Defined Benefit Plan Disclosure [Line Items]
Current year actuarial gain (loss)	$ (41)	¥ (3,446)	¥ 11,275	¥ (19,970)
Amortization of net actuarial loss	12	1,036	2,098	724
Prior service credit due to amendments	0	8	(183)	(63)
Amortization of prior service credit	(14)	(1,193)	(1,209)	(1,208)
Amortization of transition obligation	0	(4)	(3)	(3)
Plan curtailments and settlements	0	0	3	0
Foreign currency exchange rate change	2	166	69	60
Total recognized in other comprehensive income (loss), pre-tax	$ (41)	¥ (3,433)	¥ 12,050	¥ (20,460)

Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income, Foreign Exchange Adjustment

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The net prior service cost or credit recognized in other comprehensive income that is a reclassification adjustment of other comprehensive income as a result of being recognized as a component of net periodic benefit cost for the period.

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The pretax cost (credit) of benefit changes attributable to plan participants' prior service resulting from a plan amendment or plan initiation that occurred during the period. The cost has not yet been recognized in net periodic benefit cost. A plan amendment includes provisions that grant increased (decreased) benefits based on services rendered in prior periods.

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Amounts recognized in other comprehensive income (but not yet recognized in net periodic benefit cost), including the net gain (loss) and net prior service cost (credit) arising during the period. Also includes reclassification adjustments out of other comprehensive income as a result of being recognized as components of net periodic benefit cost for the period.

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Pretax change in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan, that has not been recognized in net periodic benefit cost.

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The net transition asset or obligation recognized, before tax, as a reclassification adjustment of other comprehensive income as a result of being recognized as a component of net periodic benefit cost for the period.

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