Commitments and Contingencies (Details)	1 Months Ended		3 Months Ended
	Mar. 31, 2018 USD ($) ft²	Nov. 30, 2016 USD ($)	Mar. 31, 2018 USD ($) ft² location	Mar. 31, 2017 USD ($)	Oct. 31, 2016 ft²
Future minimum lease payments
2018 (remaining 9 months)	$ 6,164,000		$ 6,164,000
2019	8,692,000		8,692,000
2020	8,825,000		8,825,000
2021	9,067,000		9,067,000
2022	9,319,000		9,319,000
2023 and thereafter	14,832,000		14,832,000
Total future minimum lease payment	$ 56,899,000		56,899,000
Rent expense			$ 2,100,000	$ 1,700,000
Corporate Headquarters Lease
Operating Leases
Office space (area) | ft²	113,000		113,000
Number of office space locations | location			2
Security Deposit	$ 700,000	$ 100,000	$ 700,000
Term of lease			84 months
Security deposit	$ 700,000	100,000	$ 700,000
Reimbursement from landlord			$ 200,000
"First Space" Sublease
Operating Leases
Office space (area) | ft²	88,000		88,000
Monthly base rent			$ 319,095
"Second Space" Sublease
Operating Leases
Office space (area) | ft²	25,000		25,000
Monthly base rent			$ 97,431
Corporate Headquarters Sublease
Operating Leases
Office space (area) | ft²					13,000
Monthly base rent		$ 49,140
Percentage of annual increase in rent		3.00%
Austin TX, Long-term Lease
Operating Leases
Office space (area) | ft²	94,000		94,000
Monthly base rent			$ 100,000
Security Deposit	$ 400,000		$ 400,000
Term of lease			132 months
Maximum monthly base rent after escalation			$ 200,000
Security deposit	400,000		400,000
Allowance for leasehold improvements	$ 7,800,000		$ 7,800,000
Tukwila, WA lease
Operating Leases
Office space (area) | ft²	10,000		10,000
Monthly base rent	$ 11,900
Term of lease	62 months
Percentage of annual increase in rent	3.00%