Commitments and Contingencies (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 31, 2015
Other Commitments [Line Items]
Term of lease	96 months
Tenant incentive					$ 1,400,000
Restricted cash		$ 0
Tenant improvement allowance used	$ 8,500,000	8,200,000
Unused tenant improvement		300,000
Rent expense		1,400,000	$ 1,200,000	$ 600,000
Deferred rent, less current portion		$ 8,072,000	8,840,000
Renewal term		5 years
Prior Lease
Other Commitments [Line Items]
Other liabilities, current			200,000
Other Noncurrent Liabilities
Other Commitments [Line Items]
Deferred rent, less current portion		$ 9,300,000	10,100,000.0
Other Noncurrent Liabilities | Prior Lease
Other Commitments [Line Items]
Deferred rent, less current portion			$ 0