Supplemental Financial Information - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental Income Statement Elements [Abstract]
Interest on revolving credit facility	$ 612	$ 1,873	$ 3,079	$ 6,303
Interest rate swap settlements	2,769	(40)	3,191	(241)
Line of credit fees	112	125	430	378
Debt issuance amortization costs	138	138	414	414
Interest on finance leases	35	29	100	92
Interest income	(135)	(398)	(724)	(1,262)
Other	22	20	49	39
Total interest expense, net	$ 3,553	$ 1,747	$ 6,539	$ 5,723

Amount of amortization expense attributable to debt issuance costs.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Amount of interest expense on finance lease liability.

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Aggregate amount of interest paid or due on all long-term debt.

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Amount of interest expense classified as other.

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The net amount of operating interest income (expense).

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Amount of interest income earned from interest bearing assets classified as other.

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Amount of the fee for available but unused credit capacity under the credit facility.

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