Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 22, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-34186
Entity Registrant Name	VANDA PHARMACEUTICALS INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	03-0491827
Entity Address, Address Line One	2200 Pennsylvania Avenue NW
Entity Address, Address Line Two	Suite 300 E
Entity Address, City or Town	Washington
Entity Address, State or Province	DC
Entity Address, Postal Zip Code	20037
City Area Code	202
Local Phone Number	734-3400
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	VNDA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		54,691,654
Entity Central Index Key	0001347178
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false