Document and Entity Information - shares	9 Months Ended
	Dec. 31, 2018	Jan. 24, 2019
Document And Entity Information
Entity Registrant Name	8X8 INC /DE/
Entity Central Index Key	0001023731
Document Type	10-Q
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Current Fiscal Year End Date	--03-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		95,654,698
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2019