Document and Entity Information - USD ($)	12 Months Ended
	Mar. 31, 2018	May 23, 2018	Sep. 30, 2017
Document And Entity Information
Entity Registrant Name	8X8 INC /DE/
Entity Central Index Key	0001023731
Document Type	10-K
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Is Entity a Well-known Seasoned Issuer?	Yes
Is Entity a Voluntary Filer?	No
Is Entity's Reporting Status Current?	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,200,000,000
Entity Common Stock, Shares Outstanding		93,004,774
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2018