| Document and Entity Information | Nov. 02, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000920465 |
| Document Type | 8-K12B |
| Document Period End Date | Nov. 2, 2021 |
| Current Fiscal Year End Date | --12-31 |
| Entity Registrant Name | LA JOLLA PHARMACEUTICAL COMPANY |
| Entity File Number | 1-36282 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 33-0361285 |
| Entity Address, Address Line One | 201 Jones Rd |
| Entity Address, Address Line Two | Suite 400 |
| Entity Address, City or Town | Waltham |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02451 |
| City Area Code | 617 |
| Local Phone Number | 715-3600 |
| 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 $0.0001 per share |
| Trading Symbol | LJPC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
