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, 2018	Dec. 31, 2017
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		$ 35,640
Fair value of plan assets at December 31,		34,263	$ 35,640
Pension Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		53,976	49,463
Service cost	[1]	715	702
Interest cost	[2]	1,855	1,961
Participant contributions		27	27
Actuarial loss (gain)		(5,725)	3,599
Benefit payments		(1,828)	(1,776)
Obligation at December 31		49,020	53,976
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of period		35,640	31,466
Actual return on plan assets		(1,925)	3,601
Employer contributions		2,349	2,322
Participant contributions		27	27
Benefit payments		(1,828)	(1,776)
Fair value of plan assets at December 31,		34,263	35,640
Funded status at end of period		(14,757)	(18,336)
Other Benefits [Member]
Reconciliation of benefit obligation:
Obligation at beginning of period		519	544
Service cost	[1]	1	1
Interest cost	[2]	18	21
Participant contributions		15	17
Actuarial loss (gain)		(36)	(22)
Benefit payments		(38)	(42)
Obligation at December 31		479	519
Reconciliation of fair value of plan assets:
Employer contributions		23	25
Participant contributions		15	17
Benefit payments		(38)	(42)
Funded status at end of period		$ (479)	$ (519)

[1] Included in general and administrative expenses.

[2] Included in other expense.