Document and Entity Information - USD ($)	12 Months Ended
	Mar. 31, 2019	May 10, 2019	Sep. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	VSAT
Entity Registrant Name	VIASAT INC
Entity Central Index Key	0000797721
Current Fiscal Year End Date	--03-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		60,597,718
Entity Public Float			$ 3,576,870,841