Leases - Lease Cost (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Operating lease cost (cost resulting from lease payments)	$ 2,601	$ 7,449
Short-term lease cost	9	29
Variable lease cost (cost excluded from lease payments)	434	1,231
Sublease income	(178)	(474)
Net lease cost	2,866	8,235
Operating lease - operating cash flows (fixed payments)	2,445	7,125
Operating lease - operating cash flows (liability reduction)	$ 1,724	$ 5,212
Weighted average lease term - operating leases (in years) (at period end)		17 years 5 months 15 days
Weighted average discount rate - operating leases (at period end)	3.41%	3.41%
Right-of-use assets obtained in exchange for new lease liabilities - operating leases	$ 14,728	$ 37,471