Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Finance lease cost
Amortization of ROU assets	$ 61	$ 59	$ 184	$ 174
Interest on lease liabilities	38	40	113	121
Operating lease cost	1,302	1,254	3,883	3,553
Short-term lease cost	93	88	261	266
Variable lease cost	264	264	759	977
Sublease income	(11)	(2)	(32)	(5)
Total lease expense	$ 1,747	$ 1,703	$ 5,168	$ 5,086

Amount of interest expense on finance lease liability.

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Amount of amortization expense attributable to right-of-use asset from finance lease.

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Amount of lease cost recognized by lessee for lease contract.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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Amount of short-term lease cost, excluding expense for lease with term of one month or less.

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Amount of sublease income excluding finance and operating lease expense.

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Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases.

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