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, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Pension assets	$ 42,835	$ 191,652	$ 180,056
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3,277	2,691
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension assets	38,220	187,601
Level 3
Defined Benefit Plan Disclosure [Line Items]
Pension assets	1,338	1,360
Fixed income bonds
Defined Benefit Plan Disclosure [Line Items]
Pension assets	27,704	186,385
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	27,704	186,385
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	3,277	2,691
Mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension assets	3,277	2,691
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	10,516	1,216
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	10,516	1,216
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	1,338	1,360
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	$ 1,338	$ 1,360