Commitments and Contingencies (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) ft² location	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Future minimum lease payments
2018	$ 8,034,000
2019	8,547,000
2020	8,675,000
2021	8,913,000
2022	9,160,000
2023 and thereafter	14,737,000
Total future minimum lease payment	58,066,000
Rent expense	$ 7,200,000	$ 5,400,000	$ 2,700,000
Corporate Headquarters Lease
Operating Leases
Office space (area) | ft²	113,000
Number of office space locations | location	2
Security Deposit	$ 700,000
Term of lease	84 months
Security deposit	$ 700,000
"First Space" Sublease
Operating Leases
Office space (area) | ft²	88,000
Monthly base rent	$ 319,095
"Second Space" Sublease
Operating Leases
Office space (area) | ft²	25,000
Monthly base rent	$ 97,431
Additional Office Space Sublease
Operating Leases
Office space (area) | ft²	13,000
Monthly base rent	$ 49,140
Security Deposit	$ 100,000
Term of lease	28 months
Percentage of annual increase in rent	3.00%
Security deposit	$ 100,000
Austin TX, Long-term Lease
Operating Leases
Office space (area) | ft²	94,000
Monthly base rent	$ 100,000
Security Deposit	$ 400,000
Term of lease	132 months
Maximum monthly base rent after escalation	$ 200,000
Security deposit	400,000
Allowance for leasehold improvements	$ 7,800,000