| Document and Entity Information | Dec. 19, 2019 |
| Cover page. | |
| Written Communications | false |
| Document Type | 8-K |
| Document Period End Date | Dec. 19, 2019 |
| Entity Registrant Name | SIMPSON MANUFACTURING CO INC /CA/ |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-13429 |
| Entity Tax Identification Number | 94-3196943 |
| Entity Address, Address | 5956 W. Las Positas Boulevard |
| 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 |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | SSD |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0000920371 |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
