Commitments and Contingencies (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) ft² location	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Future minimum lease payments
2018	$ 8,588,000
2019	8,825,000
2020	9,067,000
2021	9,319,000
2022	7,702,000
2023 and thereafter	7,130,000
Total future minimum lease payment	50,631,000
Rent expense	$ 7,400,000	$ 7,200,000	$ 5,400,000
Corporate Headquarters Lease
Operating Leases
Office space (area) | ft²	136,000
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	48,000
Monthly base rent	$ 190,424
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
Tukwila, WA lease
Operating Leases
Office space (area) | ft²	10,000
Monthly base rent	$ 11,900
Term of lease	62 months
Percentage of annual increase in rent	3.00%