Employee Benefit Plans, Financial Instruments Recorded At Fair Value On A Recurring Basis By The Plan (Details) - Pension Benefits [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 128,563	$ 122,995	$ 109,746
Recurring Basis [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	128,563	122,995
Recurring Basis [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	80,098	74,268
Recurring Basis [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,465	48,727
Recurring Basis [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,461	4,143
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,461	4,143
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	41,000	40,239
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	41,000	40,239
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	35,637	29,886
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	35,637	29,886
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | US Government Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	47	58
Recurring Basis [Member] | US Government Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | US Government Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	47	58
Recurring Basis [Member] | Corporate Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,418	48,669
Recurring Basis [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 48,418	$ 48,669