Leases - Lease cost and other information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lease Expense Components:
Amortization of ROU assets - finance leases	$ 125		$ 172
Interest on lease liabilities - finance leases	19		24
Operating lease cost (cost resulting from lease payments)	4,557	$ 2,241	9,873	$ 6,560
Short-term lease expense	253	120	450	396
Variable lease cost (cost excluded from lease payments)	370	151	739	337
Total lease cost	5,324	2,512	11,258	7,293
Supplemental Cash Flow Information Related to Leases:
Finance lease - operating cash flows	19		27
Finance lease - financing cash flows	109		150
Operating lease - operating cash flows (fixed payments)	4,307	1,996	8,763	5,804
Operating lease - operating cash flows (net change asset/liability)	(3,290)	248	(5,968)	504
New ROU assets - operating leases	$ 1,475	$ 5,289	41,211	$ 10,239
New ROU assets - finance leases			$ 5,374
Weighted - average remaining lease term (years) - finance leases	7 years 7 months 28 days		7 years 7 months 28 days
Weighted - average remaining lease term (years) - Operating leases	11 years 7 months 6 days	14 years 3 months 18 days	11 years 7 months 6 days	14 years 3 months 18 days
Weighted - average discount rate - finance leases	1.70%		1.70%
Weighted - average discount rate - Operating leases	3.30%	3.90%	3.30%	3.90%
Supplemental Balance Sheet Information Related to Leases
Operating lease ROU assets	$ 121,600		$ 121,600
Operating lease liabilities	126,058		126,058
Maturity Analysis of Lease Liabilities:
2020 (excluding the nine months ended September 30, 2020)	4,257		4,257
2021	16,381		16,381
2022	15,054		15,054
2023	14,041		14,041
2024	12,789		12,789
Thereafter	92,814		92,814
Total	155,336		155,336
Less: Imputed Interest	(29,278)		(29,278)
Lease Liability	$ 126,058		$ 126,058