Pensions and Other Employee Benefits Plans (Fair Values of Pension Plan Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 38,146	$ 34,263
Pension plans' actual assets allocation		100.00%	100.00%
Liquid Return Seeking [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans' actual assets allocation		61.00%
Liquid Return Seeking - Multi Asset Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[1]	$ 23,127	$ 20,251
Pension plans' actual assets allocation	[1]	61.00%	59.00%
Fixed Income Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plans' actual assets allocation		30.00%
Fixed Income Securities - Commingled Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[2]	$ 11,463	$ 10,869
Pension plans' actual assets allocation	[2]	30.00%	32.00%
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 3,556	$ 3,143
Pension plans' actual assets allocation		9.00%	9.00%
Alternative investments - Equity Long/Short Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[3]	$ 1,349	$ 1,002
Pension plans' actual assets allocation	[3]	4.00%	3.00%
Alternative investments - Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[4]	$ 48	$ 76
Pension plans' actual assets allocation	[4]	0.00%	0.00%
Alternative investments - Distressed Opportunity Ltd. Partnership [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[5]	$ 463	$ 463
Pension plans' actual assets allocation	[5]	1.00%	1.00%
Alternative investments - Multi-Strategy Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[6]	$ 1,696	$ 1,602
Pension plans' actual assets allocation	[6]	4.00%	5.00%
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		$ 3,556	$ 3,143	$ 3,226
Level 3 [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets		3,556	3,143
Level 3 [Member] | Alternative investments - Equity Long/Short Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[3]	1,349	1,002
Level 3 [Member] | Alternative investments - Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[4]	48	76
Level 3 [Member] | Alternative investments - Distressed Opportunity Ltd. Partnership [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[5]	463	463
Level 3 [Member] | Alternative investments - Multi-Strategy Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[6]	1,696	1,602
Assets Measured at Net Asset Value (NAV) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[7]	34,590	31,120
Assets Measured at Net Asset Value (NAV) [Member] | Liquid Return Seeking - Multi Asset Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[1],[7]	23,127	20,251
Assets Measured at Net Asset Value (NAV) [Member] | Fixed Income Securities - Commingled Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, fair value of plan assets	[2],[7]	$ 11,463	$ 10,869

[1] A single fund that invests in global equities, marketable real assets and fixed income securities. The fund has no limitation on redemptions.

[2] Investments in bonds representing many sectors of the broad bond market with both short-term and intermediate-term maturities. The fund has no limitation on redemptions.

[3] Investments primarily in long and short positions in equity securities of U.S. and non-U.S. companies. The fund generally has semi-annual tender offer redemption periods on June 30 and December 31 and is reported on a one month lag.

[4] Fund invests in portfolios of secondary interest in established venture capital, buyout, mezzanine and special situation funds on a global basis. Fund is valued on a quarterly lag with adjustment for subsequent cash activity. The fund terminates on July 12, 2020, subject to extension for up to two one-year periods. Earlier redemptions are not permitted.

[5] Investments mainly in discounted debt securities, bank loans, trade claims and other debt and equity securities of financially troubled companies. This partnership has semi-annual withdrawal rights on June 30 and December 31 with notice of 90 days and is reported on a one month lag.

[6] Investments in a partnership that has a multi-strategy investment program and does not rely on a single investment model. This partnership has quarterly redemption rights with notice of 65 days and is reported on a one month lag.

[7] Assets measured using the net asset value (“NAV”) practical expedient have not been classified in the fair value hierarchy. The NAV practical expedient is based on the fair value of the underlying assets of the common/collective trust (“CCT”) minus its liabilities, and then divided by the number of units outstanding. The NAV practical expedient of a CCT is calculated based on a compilation of primarily observable market information.