Pensions and Other Employee Benefits Plans (Components of Net Periodic Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 175	$ 167	$ 526	$ 501
Interest cost	490	495	1,470	1,486
Expected return on plan assets	(531)	(512)	(1,593)	(1,535)
Amortization of net actuarial loss	250	223	749	667
Net periodic cost	384	373	1,152	1,119
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			1	1
Interest cost	5	6	14	16
Amortization of net actuarial loss	1	1	3	4
Amortization of prior service credits	6	5	18	16
Net periodic cost	$ 12	$ 12	$ 36	$ 37