Cover
| Cover | Oct. 28, 2020 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 28, 2020 |
| Entity File Number | 001-34702 |
| Entity Registrant Name | SPS COMMERCE, INC. |
| Entity Central Index Key | 0001092699 |
| Entity Tax Identification Number | 41-2015127 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 333 South Seventh Street, Suite 1000 |
| Entity Address, City or Town | Minneapolis |
| Entity Address, State or Province | MN |
| Entity Address, Postal Zip Code | 55402 |
| City Area Code | 612 |
| Local Phone Number | 435-9400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.001 per share |
| Trading Symbol | SPSC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |