Accrued Expenses and Other Liabilities - Components of Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued product related costs	$ 3,430	$ 4,470
Accrued income taxes	6,213	7,320
Accrued property and other taxes	1,892	2,478
Accrued professional fees	1,594	1,663
Accrued customer related liabilities	4,459	3,815
Dividends payable	1,292	1,291
Remediation reserves	9,994	10,642	$ 11,444
Derivative liabilities	684	671
Other accrued liabilities	6,115	5,821
Total accrued expenses and other liabilities	$ 35,673	$ 38,171