Restructuring Plan	12 Months Ended
Dec. 31, 2018
Restructuring And Related Activities [Abstract]
Restructuring Plan	13. Restructuring Plan In October 2017, the Board of Directors of the Company approved a plan of termination to eliminate a number of positions effective October 20, 2017 (the “Restructuring Plan”), as part of its commitment to reduce costs following the failure of the Phase 3 VELOCITY trial of somavaratan to reach its primary endpoint. The reduction included 45 employees, which represented approximately 62% of its workforce as of October 6, 2017. Affected employees were notified of the Restructuring Plan on October 6, 2017. Simultaneously with the Restructuring Plan the Company established a Severance Benefit Plan (the “Plan”) for affected employees as well as a retention plan for retained employees. The Plan provides payment of severance benefits to affected employees of the Company. The Company granted approximately 907,000 restricted stock units to retained employees with a two year vesting schedule and offered a cash retention bonus of 50% of each retained employees then current base salary, which will be earned and payable subject to continued employment for an additional 12 months. Employee severance costs are accrued when the restructuring actions are probable and estimable. Costs for one-time termination benefits in which the employee is required to render service until termination in order to receive the benefits are recognized ratably over the future service period. During the year ended December 31, 2017, as a result of the Restructuring Plan, the Company incurred a one-time severance-related charge totaling $3.4 million, of which $0.7 million is included within general and administrative expenses and $2.7 million is included within research and development expenses. The Company accrued $0.8 million related to the cash retention bonus as of December 31, 2017. During the year ended December 31, 2018, the Company incurred severance-related charges totaling $4.2 million, of which $1.7 million is included within general and administrative expenses and $2.5 million is included within research and development expenses. There was no balance owed under these restructuring plans as of December 31, 2018.

Restructuring Plan

12 Months Ended

Dec. 31, 2018

Restructuring And Related Activities [Abstract]

13. Restructuring Plan

In October 2017, the Board of Directors of the Company approved a plan of termination to eliminate a number of positions effective October 20, 2017 (the “Restructuring Plan”), as part of its commitment to reduce costs following the failure of the Phase 3 VELOCITY trial of somavaratan to reach its primary endpoint. The reduction included 45 employees, which represented approximately 62% of its workforce as of October 6, 2017. Affected employees were notified of the Restructuring Plan on October 6, 2017. Simultaneously with the Restructuring Plan the Company established a Severance Benefit Plan (the “Plan”) for affected employees as well as a retention plan for retained employees. The Plan provides payment of severance benefits to affected employees of the Company. The Company granted approximately 907,000 restricted stock units to retained employees with a two year vesting schedule and offered a cash retention bonus of 50% of each retained employees then current base salary, which will be earned and payable subject to continued employment for an additional 12 months.

Employee severance costs are accrued when the restructuring actions are probable and estimable. Costs for one-time termination benefits in which the employee is required to render service until termination in order to receive the benefits are recognized ratably over the future service period. During the year ended December 31, 2017, as a result of the Restructuring Plan, the Company incurred a one-time severance-related charge totaling $3.4 million, of which $0.7 million is included within general and administrative expenses and $2.7 million is included within research and development expenses. The Company accrued $0.8 million related to the cash retention bonus as of December 31, 2017. During the year ended December 31, 2018, the Company incurred severance-related charges totaling $4.2 million, of which $1.7 million is included within general and administrative expenses and $2.5 million is included within research and development expenses. There was no balance owed under these restructuring plans as of December 31, 2018.