Retirement Plans, Pension Plan Assets (Details) - Pension Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	$ 35,676	$ 31,776	$ 28,299
Level 1 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	7,831	7,351
Level 2 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	27,845	24,425
Level 3 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
Domestic [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	6,565	6,003
Domestic [Member] | Level 1 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	6,565	6,003
Domestic [Member] | Level 2 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
Domestic [Member] | Level 3 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
International [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	97	104
International [Member] | Level 1 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
International [Member] | Level 2 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	97	104
International [Member] | Level 3 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
International Fixed Income Funds [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	28,911	25,556
International Fixed Income Funds [Member] | Level 1 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	1,190	1,269
International Fixed Income Funds [Member] | Level 2 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	27,721	24,287
International Fixed Income Funds [Member] | Level 3 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	0	0
Other Investments [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	103	113
Other Investments [Member] | Level 1 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	76	79
Other Investments [Member] | Level 2 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	27	34
Other Investments [Member] | Level 3 [Member]
Pension Plan Assets by Asset Category [Abstract]
Total assets at fair value	$ 0	$ 0