Pension Benefits, Other Postretirement Benefits and Employee Savings and Investment Plans (Assets Carried at Fair Value by Level) (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 35,296	$ 42,835	$ 191,652
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3,535	3,277
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	30,414	38,220
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	1,347	1,338
Fixed income bonds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	29,896	27,704
Fixed income bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Fixed income bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	29,896	27,704
Fixed income bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3,535	3,277
Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3,535	3,277
Mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Pension assets	518	10,516
Pooled separate accounts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Pooled separate accounts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	518	10,516
Pooled separate accounts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Guaranteed deposit account
Defined Benefit Plan Disclosure [Line Items]
Pension assets	1,347	1,338
Guaranteed deposit account | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Guaranteed deposit account | Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	0	0
Guaranteed deposit account | Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 1,347	$ 1,338