Document and Entity Information - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Nov. 02, 2021
Cover [Abstract]
Document Type		10-Q
Document Quarterly Report		true
Document Period End Date		Sep. 30, 2021
Document Transition Report		false
Entity File Number		1-13429
Entity Registrant Name		SIMPSON MANUFACTURING CO INC /CA/
Entity Incorporation, State or Country Code		DE
Entity Tax Identification Number		94-3196943
Entity Address, Address		5956 W. Las Positas Blvd.,
Entity Address, City or Town		Pleasanton
Entity Address, State or Province		CA
Entity Address, Postal Zip Code		94588
City Area Code		925
Local Phone Number		560-9000
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, par value $0.01 per share
Trading Symbol		SSD
Security Exchange Name		NYSE
Entity Common Stock, Shares Outstanding			43,439,655
Amendment Flag		false
Document Fiscal Period Focus		Q3
Document Fiscal Year Focus		2021
Entity Central Index Key		0000920371
Current Fiscal Year End Date		--12-31