Basis of Presentation and Description of Business (Policies)	3 Months Ended
	Mar. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business Activity	La Jolla Pharmaceutical Company (the "Company") is a biopharmaceutical company focused on the discovery, development and commercialization of innovative therapeutics intended to significantly improve outcomes in patients with life-threatening diseases.
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements of the Company have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 8 of the Securities and Exchange Commission (“SEC”) Regulation S-X. Accordingly, they should be read in conjunction with the audited consolidated financial statements and notes thereto for the fiscal year ended December 31, 2013, included in our Annual Report on Form 10-K filed with the SEC on March 31, 2014. The unaudited financial statements contain all normal recurring accruals and adjustments that, in the opinion of management, are necessary to present fairly the condensed balance sheets of the Company at March 31, 2014, the condensed statements of operations and comprehensive loss for the three months ended March 31, 2014, and the condensed statements of cash flows for the three months ended March 31, 2014. All intercompany accounts and transactions have been eliminated. It should be understood that accounting measurements at interim dates inherently involve greater reliance on estimates than at year end. The results of operations for the three months ended March 31, 2014 are not necessarily indicative of the results to be expected for the full year or any future interim periods.
Corporate Structure	Corporate Structure The Company was incorporated in 1989 as a Delaware corporation. In June of 2012, the Company reincorporated in the State of California. All common and preferred shares of the Delaware corporation were exchanged for common and preferred shares of the Company.
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the unaudited condensed financial statements and disclosures made in the accompanying notes to the unaudited condensed financial statements. Actual results could differ materially from those estimates.
Reverse Stock Split	Reverse Stock Split The Board of Directors approved a reverse stock split (the "2014 Reverse Stock Split") of the Company’s common stock, which became effective on January 14, 2014, with an exchange ratio of 1-for-50. As a result of the 2014 Reverse Stock Split, each 50 shares of the Company’s issued and outstanding common stock were automatically reclassified as, and changed into, one share of the Company’s common stock. No fractional shares were issued in connection with the 2014 Reverse Stock Split. Stockholders who were entitled to fractional shares instead became entitled to receive a cash payment in lieu of receiving fractional shares (after taking into account and aggregating all shares of the Company’s common stock then held by such stockholder) equal to the fractional share interest. The 2014 Reverse Stock Split affected all of the holders of the Company’s common stock uniformly. Shares of the Company’s common stock underlying outstanding options were proportionately reduced and the exercise prices of outstanding options were proportionately increased in accordance with the terms of the agreements governing such securities. Shares of the Company’s common stock underlying outstanding convertible preferred stock were proportionately reduced and the conversion rates were proportionately decreased in accordance with the terms of the agreements governing such securities. All common stock share and per share information in the accompanying unaudited condensed consolidated financial statements have been restated to reflect retrospective application of the 2014 Reverse Stock Split for all periods presented, except for par value per share and the number of authorized shares, which were not affected.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid debt instruments with an original maturity of three months or less to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts.
Net Loss Per Share	Net Loss Per Share Basic and diluted net loss per share is computed using the weighted-average number of common shares outstanding during the periods. Basic earnings per share (“EPS”) is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted EPS is computed by dividing the net loss by the weighted-average number of common shares and common stock equivalents outstanding for the period issuable upon the conversion of preferred stock and exercise of stock options and warrants. These common stock equivalents are included in the calculation of diluted EPS only if their effect is dilutive. There is no difference between basic and diluted net loss per share for the three months ended March 31, 2014. Potentially dilutive securities have been excluded from the calculation of diluted net loss per share because the inclusion of such securities would be antidilutive.
Restricted Cash	Restricted Cash Restricted cash consists of $37,000 in a certificate of deposit on hand with the Company’s financial institutions as collateral for its San Diego office space.
Property and Equipment	Property and Equipment Property and equipment is stated at cost and has been depreciated using the straight-line method over the estimated useful lives of the assets, which range from two to seven years.
Adoption of Recent Accounting Pronouncements	Adoption of Recent Accounting Pronouncements In July 2013, the FASB issued Accounting Standards Update (“ASU”) No. 2013-11, Income Taxes (Topic 740). This update improves the reporting for unrecognized tax benefits when a net operating loss carry-forward, a similar tax loss, or a tax credit carry-forward exists. The update is expected to reduce diversity in practice by providing guidance on the presentation of unrecognized tax benefits and will better reflect the manner in which an entity would settle at the reporting date any additional income taxes that would result from the disallowance of a tax position when net operating loss carry-forwards, similar tax losses, or tax credit carry-forwards exist. The update is effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013, which for us was January 1, 2014. The adoption of this update did not have a material impact on our unaudited condensed financial statements.