Cover - shares	3 Months Ended
	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-32426
Entity Registrant Name	WEX Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	01-0526993
Entity Address, Address Line One	1 Hancock St.,
Entity Address, City or Town	Portland,
Entity Address, State or Province	ME
Entity Address, Postal Zip Code	04101
City Area Code	207
Local Phone Number	773–8171
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
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	WEX
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		43,510,514
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001309108
Amendment Flag	false