Fair Value Measurements - Additional Information (Detail) (JPY ¥) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Fair Value of Financial Instruments [Line Items]
Transfers into level 1	¥ 1,612	¥ 2,169
Transfers out of level 1	¥ 2,417	¥ 7,221

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant