Document and Entity Information	6 Months Ended
	Jun. 30, 2019 shares
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
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	44,674,523
Amendment Flag	false
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2019
Entity Central Index Key	0000920371
Current Fiscal Year End Date	--12-31