Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value on a Recurring Basis [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	$ 56,628	$ 54,642
Other long-term assets		3,216
Derivative financial instruments asset	1,145
Life insurance contracts	45,453	41,707
Derivative financial instruments liability	(105)
Contingent consideration	(3,125)
Financial assets (liabilities)	99,996	99,565
Restricted current investments	21,200	8,400
Fair Value on a Recurring Basis [Member] | Level 1 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	56,628	54,642
Other long-term assets		3,216
Derivative financial instruments asset	0
Life insurance contracts	0	0
Derivative financial instruments liability	0
Contingent consideration	0
Financial assets (liabilities)	56,628	57,858
Fair Value on a Recurring Basis [Member] | Level 2 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	0	0
Other long-term assets		0
Derivative financial instruments asset	1,145
Life insurance contracts	0	0
Derivative financial instruments liability	(105)
Contingent consideration	0
Financial assets (liabilities)	1,040	0
Fair Value on a Recurring Basis [Member] | Level 3 [Member]
Financial Assets (Liabilities) [Abstract]
Cash equivalents and current investments	0	0
Other long-term assets		0
Derivative financial instruments asset	0
Life insurance contracts	45,453	41,707
Derivative financial instruments liability	0
Contingent consideration	(3,125)
Financial assets (liabilities)	42,328	41,707
Life Insurance Contracts [Member]
Changes in Fair Value of Level 3 Marketable Securities [Roll Forward]
Beginning balance	41,707	35,590
Actual return on plan assets	3,746	5,688
Purchases and issuances	0	2,003
Sales and settlements	0	(1,574)
Transfers into Level 3	0	0
Ending balance	$ 45,453	$ 41,707