Yahoo Japan Condensed Financial Information Operating Data (Detail) (Yahoo Japan, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Yahoo Japan
Schedule of Equity Method Investments [Line Items]
Revenue	$ 4,296,522	$ 4,242,623	$ 3,988,377
Gross profit	3,577,001	3,594,633	3,311,357
Income from operations	2,150,644	2,189,323	1,963,924
Net income	1,365,443	1,313,494	1,114,637
Net income attributable to Yahoo Japan	$ 1,355,457	$ 1,308,539	$ 1,108,390