Leases - Narative (Details) ft² in Thousands, $ in Millions		3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 02, 2015 ft² term_extension	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2011 ft² lease building	Jan. 01, 2019	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Length of lease						15 years
Sublease income related to facility leases				$ 6.2
Rent expense		$ 4.2	$ 8.8
Total capital leased assets, gross				94.8
Capital leases accumulated depreciation				$ 34.0
Fan Pier Leases
Property, Plant and Equipment [Line Items]
Number of leases | lease					2
Area of real estate property (in square feet) | ft²					1,100
Number of buildings under lease agreement | building					2
Length of lease					15 years
Option to extend lease term					10 years
San Diego Lease
Property, Plant and Equipment [Line Items]
Area of real estate property (in square feet) | ft²	170
Length of lease							16 years
Amount of optional renewal terms | term_extension	2
Optional renewal term length	5 years
Minimum
Property, Plant and Equipment [Line Items]
Capital lease, interest rate				1.00%
Maximum
Property, Plant and Equipment [Line Items]
Capital lease, interest rate				6.00%