Leases - Lease cost and other information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease Expense Components:
Amortization of ROU assets - finance leases	$ 47		$ 47
Interest on lease liabilities - finance leases	5		5
Operating lease expense	3,058	$ 2,173	5,316	$ 4,319
Short-term lease expense	99	132	197	276
Variable term leased expense	203	117	369	186
Total lease expense	3,412	2,422	5,934	4,781
Supplemental Cash Flow Information Related to Leases:
Finance lease - operating cash flows	8		8
Finance lease - financing cash flows	40		40
Operating lease - operating cash flows (fixed payments)	2,784	1,918	4,456	3,808
Operating lease - operating cash flows (net change asset/liability)	(2,409)	248	(2,678)	504
New ROU assets - operating leases	39,278	$ 2,994	39,736	$ 4,950
New ROU assets - finance leases	$ 5,374		$ 5,374
Weighted - average remaining lease term (years) - finance leases	10 years 7 months 17 days		10 years 7 months 17 days
Weighted - average remaining lease term (years) - Operating leases	11 years 9 months 21 days	14 years 4 months 24 days	11 years 9 months 21 days	14 years 4 months 24 days
Weighted - average discount rate - finance leases	1.90%		1.90%
Weighted - average discount rate - Operating leases	3.30%	4.00%	3.30%	4.00%
Supplemental Balance Sheet Information Related to Leases
Operating lease ROU assets	$ 123,600		$ 123,600
Operating lease liabilities	127,694		127,694
Maturity Analysis of Lease Liabilities:
2020 (excluding the six months ended June 30, 2020)	9,252		9,252
2021	16,141		16,141
2022	14,772		14,772
2023	13,808		13,808
2024	12,610		12,610
Thereafter	92,073		92,073
Total	158,656		158,656
Less: Imputed Interest	(30,962)		(30,962)
Lease Liability	$ 127,694		$ 127,694