Leases - Additional Information (Details) ft² in Thousands, $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2019	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2015 ft² term_extension	Dec. 31, 2011 ft² lease building	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
Length of lease							15 years
Sublease income related to facility leases				$ 6.2
Rent expense	$ 4.5		$ 13.3
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%
Building
Property, Plant and Equipment [Line Items]
Useful life (over)		40 years		40 years