Leases - Lease cost and other information (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lease Expense Components:
Operating lease expense	$ 2,241	$ 6,560
Short-term lease expense	120	396
Variable lease expense	151	337
Total lease expense	2,512	7,293
Supplemental Cash Flow Information Related to Leases:
Cash paid for amounts included in the measurement of lease liabilities - operating leases	1,996	5,804
ROU assets obtained in exchange for new lease liabilities during first quarter 2019- operating leases	$ 5,289	$ 10,239
Weighted - average remaining lease term (years) - Operating leases	14 years 3 months 18 days	14 years 3 months 18 days
Weighted - average discount rate - Operating leases	3.90%	3.90%
Supplemental Balance Sheet Information Related to Leases
Operating lease ROU assets	$ 89,905	$ 89,905
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net	Property, Plant and Equipment, Net
Operating lease liabilities	$ 91,039	$ 91,039
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other Liabilities	Other Liabilities