Defined Pension Plans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Pension period			30 years
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	$ (678)	$ 1,103	$ (1,096)	$ 3,159	$ 4,134
Contributions			330
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	$ 160	$ 145	$ 481	$ 435	$ 580