Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 22, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-10235
Entity Registrant Name	IDEX CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-3555336
Entity Address, Address Line One	3100 Sanders Road
Entity Address, Address Line Two	Suite 301,
Entity Address, City or Town	Northbrook,
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60062
City Area Code	847
Local Phone Number	498-7070
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	IEX
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 11,866,931,226
Entity Common Stock, Shares Outstanding		75,889,737
Documents Incorporated by Reference	Portions of the proxy statement with respect to the IDEX Corporation 2021 annual meeting of stockholders (the “2021 Proxy Statement”) are incorporated by reference into Part III of this Form 10-K.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000832101