Operating Leases - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	14 years 7 months 24 days
Operating lease right-of-use assets	$ 43,985	$ 0
Operating lease liabilities	$ 48,224	$ 0
Weighted average discount rate (as a percent)	3.55%
Minimum
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	9 months
Maximum
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	23 years