Leases - Lease cost and other information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Lease Expense Components:
Operating lease expense	$ 2,146
Short-term lease expense	144
Variable lease expense	69
Total lease expense	2,359
Supplemental Cash Flow Information Related to Leases:
Cash paid for amounts included in the measurement of lease liabilities - operating leases	1,890
Initial ROU assets recorded in exchange for new lease liabilities at January 1, 2019 - operating leases	82,160
ROU assets obtained in exchange for new lease liabilities during first quarter 2019- operating leases	$ 1,956
Weighted - average remaining lease term (years) - Operating leases	14 years 3 months 29 days
Weighted - average discount rate - Operating leases	4.00%
Supplemental Balance Sheet Information Related to Leases
Operating lease ROU assets	$ 82,787
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net
Operating lease liabilities	$ 83,043
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other Liabilities