Leases - Lease cost and other information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Lease Cost Components:
Amortization of ROU assets - finance leases	$ 117	$ 125	$ 350	$ 172
Interest on lease liabilities - finance leases	14	19	43	24
Operating lease cost (cost resulting from lease payments)	4,292	4,557	12,977	9,873
Short-term lease expense	116	253	327	450
Variable lease cost (cost excluded from lease payments)	783	370	2,073	739
Total lease cost	5,322	5,324	15,770	11,258
Supplemental Cash Flow and Other Information Related to Leases:
Finance lease - operating cash flows	14	19	43	27
Finance lease - financing cash flows	107	109	320	150
Operating lease - operating cash flows (fixed payments)	4,127	4,307	12,440	8,763
Operating lease - operating cash flows (net change asset/liability)	(3,215)	(3,290)	(9,691)	(5,968)
New ROU assets - operating leases	$ 4,196	$ 1,475	$ 5,494	41,211
New ROU assets - finance leases				$ 5,374
Weighted - average remaining lease term (years) - finance leases	6 years 7 months 28 days	7 years 7 months 28 days	6 years 7 months 28 days	7 years 7 months 28 days
Weighted - average remaining lease term (years) - Operating leases	10 years 11 months 15 days	11 years 7 months 6 days	10 years 11 months 15 days	11 years 7 months 6 days
Weighted - average discount rate - finance leases	1.70%	1.70%	1.70%	1.70%
Weighted - average discount rate - Operating leases	3.30%	3.30%	3.30%	3.30%
Maturity Analysis of Lease Liabilities:
2021 (excluding the nine months ended September 30, 2021)	$ 4,081		$ 4,081
2022	15,550		15,550
2023	14,856		14,856
2024	13,125		13,125
2025	11,597		11,597
Thereafter	82,061		82,061
Total undiscounted cash flows	141,270		141,270
Discount on cash flows	(24,909)		(24,909)
Total operating lease liabilities	$ 116,361		$ 116,361		$ 118,300