Debt - Summary of total debt (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total future principal payments	$ 70,194	$ 165,824
Less: current portion of long-term debt	(4,318)	(8,737)
Long-term debt	65,876	157,087
Notes Payable to Banks
Debt Instrument [Line Items]
Total future principal payments	$ 31,564	62,004
Notes Payable to Banks \| Equipment Note 1
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	4.16%
Term (years)	5 years
Total future principal payments	$ 0	10,643
Notes Payable to Banks \| Equipment Note 2
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	4.23%
Term (years)	7 years
Total future principal payments	$ 0	11,200
Notes Payable to Banks \| Equipment Note 3
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	3.97%
Term (years)	5 years
Total future principal payments	$ 0	1,953
Notes Payable to Banks \| Equipment Note 4
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	4.02%
Term (years)	7 years
Total future principal payments	$ 0	2,108
Notes Payable to Banks \| Equipment Note 5
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	4.01%
Term (years)	7 years
Total future principal payments	$ 0	1,751
Notes Payable to Banks \| Equipment Note 6
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	2.89%
Term (years)	7 years
Total future principal payments	$ 13,596	14,286
Notes Payable to Banks \| Equipment Note 7
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	3.09%
Term (years)	5 years
Total future principal payments	$ 7,675	9,033
Notes Payable to Banks \| Equipment Note 8
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	2.75%
Term (years)	5 years
Total future principal payments	$ 6,008	6,496
Notes Payable to Banks \| Equipment Note 9
Debt Instrument [Line Items]
Stated Interest Rate (per annum)	3.01%
Term (years)	7 years
Total future principal payments	$ 4,285	4,534
Revolving Loans
Debt Instrument [Line Items]
Term (years)	5 years
Total future principal payments	$ 38,630	$ 103,820

Contractual interest rate for funds borrowed, under the debt agreement.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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