Pensions and Other Employee Benefits Plans (Reconciliation of Changes in Plans' Benefit Obligations and Fair Value of Assets) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		$ 38,146
Fair value of plan assets at December 31,		41,457	$ 38,146
Pension Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		55,159	49,020
Service cost	[1]	703	722
Interest cost	[2]	1,765	2,018
Participant contributions		27	25
Actuarial loss (gain)		5,453	5,256
Benefit payments		(1,926)	(1,882)
Obligation at December 31		61,181	55,159
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		38,146	34,263
Actual return on plan assets		3,257	4,798
Employer contributions		1,953	942
Participant contributions		27	25
Benefit payments		(1,926)	(1,882)
Fair value of plan assets at December 31,		41,457	38,146
Funded status at end of period		(19,724)	(17,013)
Other Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		511	479
Service cost	[1]	0	0
Interest cost	[2]	17	21
Participant contributions		0	0
Actuarial loss (gain)		30	30
Benefit payments		(19)	(19)
Obligation at December 31		539	511
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		0	0
Actual return on plan assets		0	0
Employer contributions		19	19
Participant contributions		0	0
Benefit payments		(19)	(19)
Fair value of plan assets at December 31,		0	0
Funded status at end of period		$ (539)	$ (511)

[1] Included in general and administrative expenses.

[2] Included in other expense.