Supplemental Expense Information (Details) - Additional Information (Detail) (JPY ¥) In Millions, unless otherwise specified	12 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Gain on sale of fixed assets	¥ 6,693
Loss from impairment disposal of fixed assets	1,531
Disaster related losses	3,852	2,544
Related insurance income	3,144
Loss from disposal of fixed assets		¥ 844

The gains (losses) included in earnings resulting from the sale or disposal of tangible assets. This item does not include any gain (loss) recognized on the sale of oil and gas property or timber property.

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The gains (losses) included in results of operations resulting from the sale or disposal of other assets.

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Loss recognized as a result of the initial and subsequent write-down of a long-lived asset's carrying amount to fair value.

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Revenue from insurance services, including net premiums earned, gain on sale of insurance block, agency management fees and insurance contract fees and commissions.

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The charge against earnings in the period for the uninsured portion of a loss from a fire, explosion, or natural disaster (hurricane, earthquake).

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