Pensions and Other Employee Benefits Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Unfunded status at end of period	$ (15,200)
Unfunded benefit obligations, discount rate	4.25%	3.50%
Unfunded benefit obligations, decrease in discount rate	0.50%	0.50%
Change in unfunded benefit obligation as a result of decrease in half percentage point assumed discount rate	$ 3,400	$ 3,800
Accumulated pension benefit obligation	$ 48,200	53,000
Expected long-term rate of return on plan assets	7.25%
Defined Benefit Plan, Target Allocation Percentage	The target allocation within the liquid return-seeking portfolio is 75% global equities, 15% marketable real assets and 10% fixed income. Allocations may vary by up to 3% from these targets
Employee Savings (401K) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions to employee savings (401K) plan, maximum	6.00%
Participant's base salary rate	66.70%
Employer contributions	$ 100	100
Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Variance Percentage	3.00%
Global Equities[Member] | Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	75%
Marketable Real Assets[Member] | Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	15%
Fixed Income Investments [Member] | Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	10%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain) component of benefit obligation	$ 5,725	(3,599)
Contribution to qualified pension plan	2,349	2,322
Estimated employer contribution next fiscal year	900
Pension Benefits [Member] | Change in Discount Rate [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain) component of benefit obligation	5,100	3,600
Pension Benefits [Member] | Other Factors [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain) component of benefit obligation	600
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss (gain) component of benefit obligation	36	22
Contribution to qualified pension plan	$ 23	$ 25