Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 12, 2021	Jun. 30, 2020
Cover [Abstract]
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Registrant Name	LYDALL INC /DE/
Entity Central Index Key	0000060977
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	1-7665
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	06-0865505
Entity Address, Address Line One	One Colonial Road
Entity Address, City or Town	Manchester
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06042
City Area Code	860
Local Phone Number	646-1233
Title of 12(b) Security	Common Stock, $.01 par value
Trading Symbol	LDL
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 232,958,264
Entity Common Stock, Shares Outstanding		17,860,166