| Document and Entity Information | May 15, 2022 |
| Cover [Abstract] | |
| Entity Registrant Name | KEMPHARM, INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001434647 |
| Document Type | 8-K |
| Document Period End Date | May 15, 2022 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36913 |
| Entity Tax Identification Number | 20-5894398 |
| Entity Address, Address Line One | 1180 Celebration Boulevard |
| Entity Address, Address Line Two | Suite 103 |
| Entity Address, City or Town | Celebration |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 34747 |
| City Area Code | (321) |
| Local Phone Number | 939-3416 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock |
| Trading Symbol | KMPH |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
