Long-term Debt and Line of Credit - Obligations under Debt Arrangements (Details) - USD ($) $ in Thousands		1 Months Ended			12 Months Ended
	Oct. 09, 2019	May 31, 2019	Mar. 31, 2019	Jul. 31, 2018	Dec. 31, 2020	Sep. 30, 2021
Debt Instrument [Line Items]
Net Value, current					$ 4,344	$ 19,139
Net Value, long-term					29,523	$ 295
Line of Credit
Debt Instrument [Line Items]
Weighted average interest rate						2.92%
Principal current					4,500	$ 19,139
Principal, long-term					30,586	295
Principal					35,086	19,434
Deferred Issuance Costs, current					(156)
Deferred Issuance Costs, long-term					(1,063)
Debt Issuance Costs, Net, Total					(1,219)
Net Value, current					4,344	19,139
Net Value, long-term					29,523	295
Total debt					33,867	19,434
Other Debt
Debt Instrument [Line Items]
Principal current						139
Principal, long-term						295
Principal						400
Net Value, current						139
Net Value, long-term						295
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 50,000				50,000
Debt issuance expense		400
Principal current						19,000
Principal, long-term					5,000
Deferred Issuance Costs, long-term					(174)
Net Value, current						$ 19,000
Net Value, long-term					4,826
Term Loan | Line of Credit
Debt Instrument [Line Items]
Principal current					4,500
Principal, long-term					25,586
Deferred Issuance Costs, current					(156)
Deferred Issuance Costs, long-term					(889)
Net Value, current					4,344
Net Value, long-term					24,697
364-Day Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 20,000
Credit facility term					364 days
Borrowings					$ 0
Fourth, Fifth And Sixth Amendments To Credit Agreement | Term Loan | Line of Credit
Debt Instrument [Line Items]
Deferred Issuance Costs, long-term					$ (900)
Fourth Amendment to Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost				$ 900
Fifth Amendment To Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost			$ 600
Sixth Amendment To Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost		$ 900
Eighth Amendment to Credit Agreement | Line of Credit
Debt Instrument [Line Items]
Debt issuance cost	$ 0