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, 2019	Dec. 31, 2018
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		$ 34,263
Fair value of plan assets at December 31,		38,146	$ 34,263
Pension Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		49,020	53,976
Service cost	[1]	722	715
Interest cost	[2]	2,018	1,855
Participant contributions		25	27
Actuarial loss (gain)		5,256	(5,725)
Benefit payments		(1,882)	(1,828)
Obligation at December 31		55,159	49,020
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		34,263	35,640
Actual return on plan assets		4,798	(1,925)
Employer contributions		942	2,349
Participant contributions		25	27
Benefit payments		(1,882)	(1,828)
Fair value of plan assets at December 31,		38,146	34,263
Funded status at end of period		(17,013)	(14,757)
Other Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		479	519
Service cost	[1]		1
Interest cost	[2]	21	18
Participant contributions			15
Actuarial loss (gain)		30	(36)
Benefit payments		(19)	(38)
Obligation at December 31		511	479
Reconciliation of fair value of plan assets:
Employer contributions		19	23
Participant contributions			15
Benefit payments		(19)	(38)
Funded status at end of period		$ (511)	$ (479)

[1] Included in general and administrative expenses.

[2] Included in other expense.