Subsequent Event	12 Months Ended
Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event Acquisition of OMT In January 2016, the Company acquired OMT, a leader in genetic engineering of animals for the generation of human therapeutic antibodies through its OmniAb platform. OMT offers three transgenic animal platforms for license, including OmniRat®, OmniMouse® and OmniFlic®. The transaction added 16 partnered programs to the Company's portfolio. As a result of the acquisition, the Company paid $96.4 million in cash and issued $85.4 million in shares of Ligand common stock. The aggregate merger consideration is subject to certain adjustments, including amounts based on changes in OMT's net working capital and cash at closing. The Company issued 793,594 shares of its common stock based on a 20-day volume-weighted average price of $107.66 of its common stock calculated three days prior to closing. In connection with the closing of the merger, OMT's former chief executive officer, Roland Buelow, joined the Company as an employee and was granted stock options with an aggregate value of $2.0 million on the date of grant and performance stock units with an aggregate value of $18.0 million on the date of grant. Dr. Buelow's performance stock units will vest based on achievement of certain milestones related to the OMT business, including annual revenues, research and development milestones and entering into new business releationships. Dr. Buelow also entered into a noncompetition agreement with the Company pursuant to which he agreed not to engage in any competitive activities for a period of two years following the merger. Due to the close proximity of the acquisition date and the Company’s filing of its annual report on Form 10-K for the year ended December 31, 2015, the initial accounting for the business combination is incomplete, and therefore the Company is unable to disclose the information required by ASC 805, Business Combinations. Such information will be included in the Company’s subsequent Form 10-Q. Viking Note Amendment In January 2016, the Company entered into a second amendment to the LSA with Viking. The Company provided Viking with loans in an aggregate amount of $2.5 million, evidenced by a Secured Convertible Promissory Note. The loan amendment extends the maturity date of the loans under the Viking Note from May 21, 2016 to May 21, 2017, reduces the annual interest rate from 5.0% to 2.5%, and extends the Company’s lock-up period by one year such that the Company may not, sell or otherwise transfer or dispose of any Viking securities prior to January 23, 2017. Additionally, upon the consummation of Viking’s first capital financing transaction, Viking will be required to repay $1.5 million of the Viking Note obligation to the Company, with at least $0.3 million to be paid in cash and the remaining amount to be paid in the form of shares of Viking’s equity securities.

Subsequent Event

Acquisition of OMT

In January 2016, the Company acquired OMT, a leader in genetic engineering of animals for the generation of human therapeutic antibodies through its OmniAb platform. OMT offers three transgenic animal platforms for license, including OmniRat®, OmniMouse® and OmniFlic®. The transaction added 16 partnered programs to the Company's portfolio. As a result of the acquisition, the Company paid $96.4 million in cash and issued $85.4 million in shares of Ligand common stock. The aggregate merger consideration is subject to certain adjustments, including amounts based on changes in OMT's net working capital and cash at closing. The Company issued 793,594 shares of its common stock based on a 20-day volume-weighted average price of $107.66 of its common stock calculated three days prior to closing.

In connection with the closing of the merger, OMT's former chief executive officer, Roland Buelow, joined the Company as an employee and was granted stock options with an aggregate value of $2.0 million on the date of grant and performance stock units with an aggregate value of $18.0 million on the date of grant. Dr. Buelow's performance stock units will vest based on achievement of certain milestones related to the OMT business, including annual revenues, research and development milestones and entering into new business releationships. Dr. Buelow also entered into a noncompetition agreement with the Company pursuant to which he agreed not to engage in any competitive activities for a period of two years following the merger.

Due to the close proximity of the acquisition date and the Company’s filing of its annual report on Form 10-K for the year ended December 31, 2015, the initial accounting for the business combination is incomplete, and therefore the Company is unable to disclose the information required by ASC 805, Business Combinations. Such information will be included in the Company’s subsequent Form 10-Q.

Viking Note Amendment

In January 2016, the Company entered into a second amendment to the LSA with Viking. The Company provided Viking with loans in an aggregate amount of $2.5 million, evidenced by a Secured Convertible Promissory Note. The loan amendment extends the maturity date of the loans under the Viking Note from May 21, 2016 to May 21, 2017, reduces the annual interest rate from 5.0% to 2.5%, and extends the Company’s lock-up period by one year such that the Company may not, sell or otherwise transfer or dispose of any Viking securities prior to January 23, 2017. Additionally, upon the consummation of Viking’s first capital financing transaction, Viking will be required to repay $1.5 million of the Viking Note obligation to the Company, with at least $0.3 million to be paid in cash and the remaining amount to be paid in the form of shares of Viking’s equity securities.