Leases - Lease Asset and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Right-of-use assets - operating leases	$ 164,659	$ 146,000	$ 0
Lease liabilities - operating leases	205,167	$ 178,000	$ 0
SVB Leerink Segment
Lessee, Lease, Description [Line Items]
Right-of-use assets - operating leases	24,400
Lease liabilities - operating leases	$ 33,700