Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	May 31, 2020	Dec. 31, 2019	Oct. 31, 2016
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use asset	$ 28,943		$ 28,943			$ 27,532
Operating lease liability	30,300		30,300
Operating lease liability, current	7,200		7,200
Operating lease liability, noncurrent	$ 23,200		$ 23,200
Weighted average minimum lease term			2 years 6 months
Weighted average discount rate	5.97%		5.97%
Total operating lease costs	$ 2,400	$ 2,700	$ 5,500	$ 5,300
Cash paid, lease liabilities, operating leases	$ 2,100	$ 2,600	$ 4,400	$ 5,200
Cologne, Germany
Lessee, Lease, Description [Line Items]
Undiscounted future lease payments					$ 6,000		$ 35,000
Undiscounted future lease payments, term of lease					10 years		20 years