Long Term Obligations - San Diego Lease (Details) ft² in Thousands, $ in Thousands	Dec. 02, 2015 USD ($) ft² term	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Property and equipment, net		$ 789,437	$ 698,362
San Diego Leases
Property, Plant and Equipment [Line Items]
Area of real estate property (in square feet) | ft²	170
Length of lease	16 years
Average yearly aggregate rent	$ 10,200
Amount of optional renewal terms | term	2
Optional renewal term length	5 years
Construction financing lease obligation, current and noncurrent		87,400	12,600
Construction in Progress | San Diego Leases
Property, Plant and Equipment [Line Items]
Property and equipment, net		$ 94,600	$ 15,000