401(k) Plan	12 Months Ended
Dec. 31, 2018
Postemployment Benefits [Abstract]
401(k) Plan	15. 401(k) Plan The Company maintains a 401(k) retirement savings plan (the “Plan”) whereby employees may elect to defer a portion of their salary and contribute the deferred portion to the Plan. The Company contributes an amount equal to 50% of the employee’s contribution to the Plan, up to an annual limit of $3 in 2018 and $2 for 2017 and 2016. The Company contributed $1.1 million, $0.9 million and $0.9 million to the Plan for each of the years ended December 31, 2018, 2017, and 2016 respectively. Employee contributions and the Company’s matching contributions are invested in one or more collective investment funds at the participant’s direction. The Company’s matching contributions vest 25% annually and are 100% vested after four consecutive years of service.

The entire disclosure of an entity's employee compensation and benefit plans, excluding share-based compensation and including, but not limited to, postemployment and postretirement benefit plans, defined benefit pension plans, defined contribution plans, non-qualified and supplemental benefit plans, deferred compensation, life insurance, severance, health care, unemployment and other benefit plans.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 712
-URI http://asc.fasb.org/topic&trid=2197446

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-URI http://asc.fasb.org/topic&trid=2235017

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-URI http://asc.fasb.org/topic&trid=2127225

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