Collaboration and Licensing Agreements	12 Months Ended
Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and Licensing Agreements	7. COLLABORATION AND LICENSING AGREEMENTS *AstraZeneca AB (“AstraZeneca”)* In October 2012, the Company entered into a collaboration partnership with AstraZeneca for the worldwide development and commercialization of tenapanor. Under the terms of the AstraZeneca collaboration partnership agreement, or the AstraZeneca Agreement, the Company received an aggregate of $75 million in up-front license and milestone fees. The amounts were recorded as deferred revenue when received and were recognized as revenue on a straight-line basis over the remaining estimated period of performance under the AstraZeneca Agreement. In June 2015, the Company entered into a termination agreement with AstraZeneca (the “Termination Agreement”) pursuant to which all licenses granted to AstraZeneca to the Company’s portfolio of NHE3 inhibitors, including the Company’s lead product candidate, tenapanor, were terminated, except for the limited purpose of allowing AstraZeneca to satisfy its obligations under the Termination Agreement. As the AstraZeneca Agreement was terminated in June 2015, the Company recognized the remaining deferred revenue balance of $43.1 million during the three months ended June 30, 2015. In the three months ended June 30, 2015, the Company recorded a $15.0 million payment for the return of the licenses as well as a $10.0 million payment for reimbursement of research and development expenses and the acceleration of the transfer of information and materials as a reduction in licensing revenue in the consolidated statements of operations. There has been no recognition of licensing revenue or collaborative development revenue since the termination of the AstraZeneca agreement in 2015. *Sanofi SA (“Sanofi”)* In February 2014, the Company entered into a license option and license agreement with Sanofi (the “Sanofi Agreement”) for its phosphate transport NaP2b inhibitor program. Under the terms of the Sanofi Agreement, the Company granted Sanofi an exclusive worldwide license to conduct research utilizing the Company’s small molecule NaP2b inhibitors. In addition, Sanofi had the option to obtain an exclusive license to develop, manufacture and commercialize potential products under the agreement. Under the Sanofi Agreement, the Company received a payment of $1.25 million in March 2014, which was fully recognized as licensing revenue in May 2014 after the Company completed its obligation to provide to Sanofi the background know-how, listed patents, and materials described in the Sanofi Agreement. The Sanofi Agreement was terminated effective September 30, 2015 and all rights were returned to the Company. There was no payment associated with termination and the return of rights to the Company.

7. COLLABORATION AND LICENSING AGREEMENTS

AstraZeneca AB (“AstraZeneca”)

In October 2012, the Company entered into a collaboration partnership with AstraZeneca for the worldwide development and commercialization of tenapanor. Under the terms of the AstraZeneca collaboration partnership agreement, or the AstraZeneca Agreement, the Company received an aggregate of $75 million in up-front license and milestone fees. The amounts were recorded as deferred revenue when received and were recognized as revenue on a straight-line basis over the remaining estimated period of performance under the AstraZeneca Agreement.

In June 2015, the Company entered into a termination agreement with AstraZeneca (the “Termination Agreement”) pursuant to which all licenses granted to AstraZeneca to the Company’s portfolio of NHE3 inhibitors, including the Company’s lead product candidate, tenapanor, were terminated, except for the limited purpose of allowing AstraZeneca to satisfy its obligations under the Termination Agreement. As the AstraZeneca Agreement was terminated in June 2015, the Company recognized the remaining deferred revenue balance of $43.1 million during the three months ended June 30, 2015. In the three months ended June 30, 2015, the Company recorded a $15.0 million payment for the return of the licenses as well as a $10.0 million payment for reimbursement of research and development expenses and the acceleration of the transfer of information and materials as a reduction in licensing revenue in the consolidated statements of operations. There has been no recognition of licensing revenue or collaborative development revenue since the termination of the AstraZeneca agreement in 2015.

Sanofi SA (“Sanofi”)

In February 2014, the Company entered into a license option and license agreement with Sanofi (the “Sanofi Agreement”) for its phosphate transport NaP2b inhibitor program. Under the terms of the Sanofi Agreement, the Company granted Sanofi an exclusive worldwide license to conduct research utilizing the Company’s small molecule NaP2b inhibitors. In addition, Sanofi had the option to obtain an exclusive license to develop, manufacture and commercialize potential products under the agreement. Under the Sanofi Agreement, the Company received a payment of $1.25 million in March 2014, which was fully recognized as licensing revenue in May 2014 after the Company completed its obligation to provide to Sanofi the background know-how, listed patents, and materials described in the Sanofi Agreement.

The Sanofi Agreement was terminated effective September 30, 2015 and all rights were returned to the Company. There was no payment associated with termination and the return of rights to the Company.