Benefit Plans (Information about Level 3 Assets Measured at Fair Value on Recurring Basis) (Detail) - Domestic Pension Plans - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	¥ 197,398	¥ 183,003
Actual return on plan assets:
Fair value of plan assets at end of year	202,368	197,398
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	25,162	17,525
Actual return on plan assets:
Relating to assets still held at end of year	2,050	1,607
Relating to assets sold during the year	0	0
Purchases, sales and settlements	5,919	6,030
Transfers into level 3	1,412
Fair value of plan assets at end of year	¥ 34,543	¥ 25,162

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Actual return on plan assets, separately identifying the amount related to assets sold during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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Actual return on plan assets, separately identifying the amount related to assets still held at the reporting date.

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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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No definition available.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930

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Amount of increase (decrease) in plan assets from purchases, sales and settlement of plan obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
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Transfers in and out of Level 3. For example, transfers due to changes in the observability of significant inputs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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