| 金銭の信託運用益 | ja | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| 金銭の信託運用益、経常収益、銀行業 | ja | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| (うち金銭の信託運用益) | ja | http://disclosure.edinet-fsa.go.jp/jppfs/bnk/role/label | http://www.xbrl.org/2003/role/link |
| Gain on money held in trust | en | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Gain on money held in trust-OI-BNK | en | http://www.xbrl.org/2003/role/verboseLabel | http://www.xbrl.org/2003/role/link |
| Gain on money held in trust | en | http://disclosure.edinet-fsa.go.jp/jppfs/bnk/role/label | http://www.xbrl.org/2003/role/link |