Leases - Lease Asset and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Right-of-use assets - operating leases	$ 178,532	$ 146,000	$ 0
Lease liabilities - operating leases	192,543	$ 178,000	$ 0
SVB Leerink
Lessee, Lease, Description [Line Items]
Right-of-use assets - operating leases	22,800
Lease liabilities - operating leases	$ 31,400