Leases - Lease cost and other information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lease Expense Components:
Operating lease expense	$ 2,258	$ 2,146
Short-term lease expense	98	144
Variable term leased expense	166	69
Total lease expense	2,522	2,359
Supplemental Cash Flow Information Related to Leases:
Cash paid for amounts included in the measurement of lease liabilities - operating leases	1,672	1,890
Initial ROU assets recorded in exchange for new lease liabilities - operating leases	$ 458	$ 1,956
Weighted - average remaining lease term (years) - Operating leases	13 years 11 months 1 day	14 years 3 months 29 days
Weighted - average discount rate - Operating leases	3.90%	4.00%
Supplemental Balance Sheet Information Related to Leases
Operating lease ROU assets	$ 86,437	$ 82,787
Operating lease liabilities	88,163	83,043
Maturity Analysis of Lease Liabilities:
2020 (excluding the three months ended March 31, 2020)	6,132
2021	8,276
2022	8,392
2023	8,466
2024	8,026
Thereafter	76,498
Total	115,790
Less: Imputed Interest	(27,627)
Lease Liability	$ 88,163	$ 83,043