Retirement Plan	12 Months Ended
Dec. 31, 2017
Retirement Benefits [Abstract]
Retirement Plan	Retirement Plan The Company has a 401(k) defined contribution plan for the benefit for all US employees and permits voluntary contributions by employees subject to IRS-imposed limitations. Beginning in April 2015, the Company matched 100% of eligible employee contributions on the first 3% of employee salary (up to the IRS maximum). Employer contributions for the year ended December 31, 2017, 2016 and 2015 were $0.8 million, $0.6 million and $0.4 million, respectively. Effective January 1, 2018, the Company is matching 100% of eligible employee contributions on the first 4% of employee salary (up to the IRS maximum).

Retirement Plan

12 Months Ended

Dec. 31, 2017

The Company has a 401(k) defined contribution plan for the benefit for all US employees and permits voluntary contributions by employees subject to IRS-imposed limitations. Beginning in April 2015, the Company matched 100% of eligible employee contributions on the first 3% of employee salary (up to the IRS maximum). Employer contributions for the year ended December 31, 2017, 2016 and 2015 were $0.8 million, $0.6 million and $0.4 million, respectively. Effective January 1, 2018, the Company is matching 100% of eligible employee contributions on the first 4% of employee salary (up to the IRS maximum).